diff --git a/docs/conf.py b/docs/conf.py
index 35746dd77..a4b1caf2f 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -40,7 +40,7 @@
 
 # General information about the project.
 project = 'Borg - Deduplicating Archiver'
-copyright = u'2010-2014 Jonas Borgström, 2015-2022 The Borg Collective (see AUTHORS file)'
+copyright = '2010-2014 Jonas Borgström, 2015-2022 The Borg Collective (see AUTHORS file)'
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the
diff --git a/scripts/glibc_check.py b/scripts/glibc_check.py
index 44fd25cd1..5f8344960 100755
--- a/scripts/glibc_check.py
+++ b/scripts/glibc_check.py
@@ -35,12 +35,12 @@ def main():
             output = subprocess.check_output(objdump % filename, shell=True,
                                              stderr=subprocess.STDOUT)
             output = output.decode()
-            versions = set(parse_version(match.group(1))
-                           for match in glibc_re.finditer(output))
+            versions = {parse_version(match.group(1))
+                        for match in glibc_re.finditer(output)}
             requires_glibc = max(versions)
             overall_versions.add(requires_glibc)
             if verbose:
-                print("%s %s" % (filename, format_version(requires_glibc)))
+                print(f"{filename} {format_version(requires_glibc)}")
         except subprocess.CalledProcessError:
             if verbose:
                 print("%s errored." % filename)
diff --git a/scripts/py36-blake2.py b/scripts/py36-blake2.py
index 758a4f346..fff13b588 100644
--- a/scripts/py36-blake2.py
+++ b/scripts/py36-blake2.py
@@ -1,4 +1,3 @@
-
 """
 This script checks compatibility of crypto.blake2b_256 against hashlib.blake2b in CPython 3.6.
 """
diff --git a/setup_docs.py b/setup_docs.py
index d326ec8d2..9513604bb 100644
--- a/setup_docs.py
+++ b/setup_docs.py
@@ -12,7 +12,7 @@
 
 
 def long_desc_from_readme():
-    with open('README.rst', 'r') as fd:
+    with open('README.rst') as fd:
         long_description = fd.read()
         # remove header, but have one \n before first headline
         start = long_description.find('What is BorgBackup?')
@@ -33,7 +33,7 @@ def format_metavar(option):
     elif option.nargs is None:
         return option.metavar
     else:
-        raise ValueError('Can\'t format metavar %s, unknown nargs %s!' % (option.metavar, option.nargs))
+        raise ValueError(f'Can\'t format metavar {option.metavar}, unknown nargs {option.nargs}!')
 
 
 class build_usage(Command):
@@ -367,7 +367,7 @@ def generate_level(self, prefix, parser, Archiver, extra_choices=None):
                 subparsers = [action for action in parser._actions if 'SubParsersAction' in str(action.__class__)][0]
                 for subcommand in subparsers.choices:
                     write('| borg', '[common options]', command, subcommand, '...')
-                    self.see_also.setdefault(command, []).append('%s-%s' % (command, subcommand))
+                    self.see_also.setdefault(command, []).append(f'{command}-{subcommand}')
             else:
                 if command == "borgfs":
                     write(command, end='')
diff --git a/src/borg/archive.py b/src/borg/archive.py
index 1c6f1ac09..279a0e131 100644
--- a/src/borg/archive.py
+++ b/src/borg/archive.py
@@ -198,7 +198,7 @@ def __init__(self, op, os_error):
 
     def __str__(self):
         if self.op:
-            return '%s: %s' % (self.op, self.os_error)
+            return f'{self.op}: {self.os_error}'
         else:
             return str(self.os_error)
 
@@ -464,7 +464,7 @@ def __init__(self, repository, key, manifest, name, cache=None, create=False,
                 raise self.AlreadyExists(name)
             i = 0
             while True:
-                self.checkpoint_name = '%s.checkpoint%s' % (name, i and ('.%d' % i) or '')
+                self.checkpoint_name = '{}.checkpoint{}'.format(name, i and ('.%d' % i) or '')
                 if self.checkpoint_name not in manifest.archives:
                     break
                 i += 1
@@ -1823,7 +1823,7 @@ def replacement_chunk(size):
             chunks_healthy = item.chunks_healthy if has_chunks_healthy else chunks_current
             if has_chunks_healthy and len(chunks_current) != len(chunks_healthy):
                 # should never happen, but there was issue #3218.
-                logger.warning('{}: {}: Invalid chunks_healthy metadata removed!'.format(archive_name, item.path))
+                logger.warning(f'{archive_name}: {item.path}: Invalid chunks_healthy metadata removed!')
                 del item.chunks_healthy
                 has_chunks_healthy = False
                 chunks_healthy = chunks_current
@@ -1867,7 +1867,7 @@ def replacement_chunk(size):
                 # if this is first repair, remember the correct chunk IDs, so we can maybe heal the file later
                 item.chunks_healthy = item.chunks
             if has_chunks_healthy and chunk_list == chunks_healthy:
-                logger.info('{}: {}: Completely healed previously damaged file!'.format(archive_name, item.path))
+                logger.info(f'{archive_name}: {item.path}: Completely healed previously damaged file!')
                 del item.chunks_healthy
             item.chunks = chunk_list
             if 'size' in item:
@@ -1902,7 +1902,7 @@ def report(msg, chunk_id, chunk_no):
                 logger.error(msg)
 
             def list_keys_safe(keys):
-                return ', '.join((k.decode(errors='replace') if isinstance(k, bytes) else str(k) for k in keys))
+                return ', '.join(k.decode(errors='replace') if isinstance(k, bytes) else str(k) for k in keys)
 
             def valid_item(obj):
                 if not isinstance(obj, StableDict):
@@ -1972,7 +1972,7 @@ def valid_item(obj):
         with cache_if_remote(self.repository) as repository:
             for i, info in enumerate(archive_infos):
                 pi.show(i)
-                logger.info('Analyzing archive {} ({}/{})'.format(info.name, i + 1, num_archives))
+                logger.info(f'Analyzing archive {info.name} ({i + 1}/{num_archives})')
                 archive_id = info.id
                 if archive_id not in self.chunks:
                     logger.error('Archive metadata block is missing!')
@@ -2008,7 +2008,7 @@ def orphan_chunks_check(self):
             unused = {id_ for id_, entry in self.chunks.iteritems() if entry.refcount == 0}
             orphaned = unused - self.possibly_superseded
             if orphaned:
-                logger.error('{} orphaned objects found!'.format(len(orphaned)))
+                logger.error(f'{len(orphaned)} orphaned objects found!')
                 self.error_found = True
             if self.repair and unused:
                 logger.info('Deleting %d orphaned and %d superseded objects...' % (
diff --git a/src/borg/archiver.py b/src/borg/archiver.py
index 1302bf916..be2b4c5c4 100644
--- a/src/borg/archiver.py
+++ b/src/borg/archiver.py
@@ -377,7 +377,7 @@ def do_key_export(self, args, repository):
                 else:
                     manager.export(args.path)
             except IsADirectoryError:
-                self.print_error("'{}' must be a file, not a directory".format(args.path))
+                self.print_error(f"'{args.path}' must be a file, not a directory")
                 return EXIT_ERROR
         return EXIT_SUCCESS
 
@@ -1191,7 +1191,7 @@ def _delete_archives(self, args, repository):
                     current_archive = manifest.archives.pop(archive_name)
                 except KeyError:
                     self.exit_code = EXIT_WARNING
-                    logger.warning('Archive {} not found ({}/{}).'.format(archive_name, i, len(archive_names)))
+                    logger.warning(f'Archive {archive_name} not found ({i}/{len(archive_names)}).')
                 else:
                     deleted = True
                     if self.output_list:
@@ -1851,12 +1851,12 @@ def list_config(config):
                     value = default_values.get(key)
                     if value is None:
                         raise Error('The repository config is missing the %s key which has no default value' % key)
-                print('%s = %s' % (key, value))
+                print(f'{key} = {value}')
             for key in ['last_segment_checked', ]:
                 value = config.get('repository', key, fallback=None)
                 if value is None:
                     continue
-                print('%s = %s' % (key, value))
+                print(f'{key} = {value}')
 
         if not args.list:
             if args.name is None:
@@ -2059,7 +2059,7 @@ def do_debug_search_repo_objs(self, args, repository):
         def print_finding(info, wanted, data, offset):
             before = data[offset - context:offset]
             after = data[offset + len(wanted):offset + len(wanted) + context]
-            print('%s: %s %s %s == %r %r %r' % (info, before.hex(), wanted.hex(), after.hex(),
+            print('{}: {} {} {} == {!r} {!r} {!r}'.format(info, before.hex(), wanted.hex(), after.hex(),
                                                 before, wanted, after))
 
         wanted = args.wanted
@@ -5032,7 +5032,7 @@ def sig_info_handler(sig_no, stack):  # pragma: no cover
                     total = loc['st'].st_size
                 except Exception:
                     pos, total = 0, 0
-                logger.info("{0} {1}/{2}".format(path, format_file_size(pos), format_file_size(total)))
+                logger.info(f"{path} {format_file_size(pos)}/{format_file_size(total)}")
                 break
             if func in ('extract_item', ):  # extract op
                 path = loc['item'].path
@@ -5040,7 +5040,7 @@ def sig_info_handler(sig_no, stack):  # pragma: no cover
                     pos = loc['fd'].tell()
                 except Exception:
                     pos = 0
-                logger.info("{0} {1}/???".format(path, format_file_size(pos)))
+                logger.info(f"{path} {format_file_size(pos)}/???")
                 break
 
 
@@ -5078,7 +5078,7 @@ def main():  # pragma: no cover
         except Error as e:
             msg = e.get_message()
             tb_log_level = logging.ERROR if e.traceback else logging.DEBUG
-            tb = '%s\n%s' % (traceback.format_exc(), sysinfo())
+            tb = f'{traceback.format_exc()}\n{sysinfo()}'
             # we might not have logging setup yet, so get out quickly
             print(msg, file=sys.stderr)
             if tb_log_level == logging.ERROR:
@@ -5091,7 +5091,7 @@ def main():  # pragma: no cover
             msg = e.get_message()
             msgid = type(e).__qualname__
             tb_log_level = logging.ERROR if e.traceback else logging.DEBUG
-            tb = "%s\n%s" % (traceback.format_exc(), sysinfo())
+            tb = f"{traceback.format_exc()}\n{sysinfo()}"
             exit_code = e.exit_code
         except RemoteRepository.RPCError as e:
             important = e.exception_class not in ('LockTimeout', ) and e.traceback
@@ -5108,18 +5108,18 @@ def main():  # pragma: no cover
             msg = 'Local Exception'
             msgid = 'Exception'
             tb_log_level = logging.ERROR
-            tb = '%s\n%s' % (traceback.format_exc(), sysinfo())
+            tb = f'{traceback.format_exc()}\n{sysinfo()}'
             exit_code = EXIT_ERROR
         except KeyboardInterrupt:
             msg = 'Keyboard interrupt'
             tb_log_level = logging.DEBUG
-            tb = '%s\n%s' % (traceback.format_exc(), sysinfo())
+            tb = f'{traceback.format_exc()}\n{sysinfo()}'
             exit_code = EXIT_SIGNAL_BASE + 2
         except SigTerm:
             msg = 'Received SIGTERM'
             msgid = 'Signal.SIGTERM'
             tb_log_level = logging.DEBUG
-            tb = '%s\n%s' % (traceback.format_exc(), sysinfo())
+            tb = f'{traceback.format_exc()}\n{sysinfo()}'
             exit_code = EXIT_SIGNAL_BASE + 15
         except SigHup:
             msg = 'Received SIGHUP.'
diff --git a/src/borg/cache.py b/src/borg/cache.py
index 6f6d87514..92df82e11 100644
--- a/src/borg/cache.py
+++ b/src/borg/cache.py
@@ -83,7 +83,7 @@ def key_matches(self, key):
         if not self.known():
             return False
         try:
-            with open(self.key_type_file, 'r') as fd:
+            with open(self.key_type_file) as fd:
                 type = fd.read()
                 return type == str(key.TYPE)
         except OSError as exc:
@@ -687,13 +687,13 @@ def cached_archives():
                 fns = os.listdir(archive_path)
                 # filenames with 64 hex digits == 256bit,
                 # or compact indices which are 64 hex digits + ".compact"
-                return set(unhexlify(fn) for fn in fns if len(fn) == 64) | \
-                       set(unhexlify(fn[:64]) for fn in fns if len(fn) == 72 and fn.endswith('.compact'))
+                return {unhexlify(fn) for fn in fns if len(fn) == 64} | \
+                       {unhexlify(fn[:64]) for fn in fns if len(fn) == 72 and fn.endswith('.compact')}
             else:
                 return set()
 
         def repo_archives():
-            return set(info.id for info in self.manifest.archives.list())
+            return {info.id for info in self.manifest.archives.list()}
 
         def cleanup_outdated(ids):
             for id in ids:
diff --git a/src/borg/crypto/file_integrity.py b/src/borg/crypto/file_integrity.py
index 84b22a7e0..87518a2a7 100644
--- a/src/borg/crypto/file_integrity.py
+++ b/src/borg/crypto/file_integrity.py
@@ -224,7 +224,7 @@ def integrity_file_path(path):
     @classmethod
     def read_integrity_file(cls, path):
         try:
-            with open(cls.integrity_file_path(path), 'r') as fd:
+            with open(cls.integrity_file_path(path)) as fd:
                 return cls.parse_integrity_data(path, fd.read())
         except FileNotFoundError:
             logger.info('No integrity file found for %s', path)
diff --git a/src/borg/crypto/key.py b/src/borg/crypto/key.py
index ff0aa93cd..0cc487ab8 100644
--- a/src/borg/crypto/key.py
+++ b/src/borg/crypto/key.py
@@ -379,7 +379,7 @@ def decrypt(self, id, data, decompress=True):
         try:
             payload = self.cipher.decrypt(data)
         except IntegrityError as e:
-            raise IntegrityError("Chunk %s: Could not decrypt [%s]" % (bin_to_hex(id), str(e)))
+            raise IntegrityError(f"Chunk {bin_to_hex(id)}: Could not decrypt [{str(e)}]")
         if not decompress:
             return payload
         data = self.decompress(payload)
@@ -469,7 +469,7 @@ def getpass(cls, prompt):
             msg = []
             for env_var in 'BORG_PASSPHRASE', 'BORG_PASSCOMMAND':
                 env_var_set = os.environ.get(env_var) is not None
-                msg.append('%s is %s.' % (env_var, 'set' if env_var_set else 'not set'))
+                msg.append('{} is {}.'.format(env_var, 'set' if env_var_set else 'not set'))
             msg.append('Interactive password query failed.')
             raise NoPassphraseFailure(' '.join(msg)) from None
         else:
@@ -760,7 +760,7 @@ def _get_new_target_in_keys_dir(self, args):
         return path
 
     def load(self, target, passphrase):
-        with open(target, 'r') as fd:
+        with open(target) as fd:
             key_data = ''.join(fd.readlines()[1:])
         success = self._load(key_data, passphrase)
         if success:
@@ -775,7 +775,7 @@ def save(self, target, passphrase, create=False):
             raise Error('Aborting because key in "%s" already exists.' % target)
         key_data = self._save(passphrase)
         with SaveFile(target) as fd:
-            fd.write('%s %s\n' % (self.FILE_ID, bin_to_hex(self.repository_id)))
+            fd.write(f'{self.FILE_ID} {bin_to_hex(self.repository_id)}\n')
             fd.write(key_data)
             fd.write('\n')
         self.target = target
diff --git a/src/borg/crypto/keymanager.py b/src/borg/crypto/keymanager.py
index 675c57635..32dd39c04 100644
--- a/src/borg/crypto/keymanager.py
+++ b/src/borg/crypto/keymanager.py
@@ -52,7 +52,7 @@ def load_keyblob(self):
         if self.keyblob_storage == KeyBlobStorage.KEYFILE:
             k = KeyfileKey(self.repository)
             target = k.find_key()
-            with open(target, 'r') as fd:
+            with open(target) as fd:
                 self.keyblob = ''.join(fd.readlines()[1:])
 
         elif self.keyblob_storage == KeyBlobStorage.REPO:
@@ -68,7 +68,7 @@ def store_keyblob(self, args):
             self.repository.save_key(self.keyblob.encode('utf-8'))
 
     def get_keyfile_data(self):
-        data = '%s %s\n' % (KeyfileKey.FILE_ID, bin_to_hex(self.repository.id))
+        data = f'{KeyfileKey.FILE_ID} {bin_to_hex(self.repository.id)}\n'
         data += self.keyblob
         if not self.keyblob.endswith('\n'):
             data += '\n'
@@ -115,7 +115,7 @@ def grouped(s):
         lines = (len(binary) + 17) // 18
         repoid = bin_to_hex(self.repository.id)[:18]
         complete_checksum = sha256_truncated(binary, 12)
-        export += 'id: {0:d} / {1} / {2} - {3}\n'.format(lines,
+        export += 'id: {:d} / {} / {} - {}\n'.format(lines,
                                        grouped(repoid),
                                        grouped(complete_checksum),
                                        sha256_truncated((str(lines) + '/' + repoid + '/' + complete_checksum).encode('ascii'), 2))
@@ -124,7 +124,7 @@ def grouped(s):
             idx += 1
             binline = binary[:18]
             checksum = sha256_truncated(idx.to_bytes(2, byteorder='big') + binline, 2)
-            export += '{0:2d}: {1} - {2}\n'.format(idx, grouped(bin_to_hex(binline)), checksum)
+            export += f'{idx:2d}: {grouped(bin_to_hex(binline))} - {checksum}\n'
             binary = binary[18:]
 
         with dash_open(path, 'w') as fd:
@@ -188,7 +188,7 @@ def import_paperkey(self, args):
                 idx = 1
                 # body line input
                 while True:
-                    inline = input('{0:2d}: '.format(idx))
+                    inline = input(f'{idx:2d}: ')
                     inline = inline.replace(' ', '')
                     if inline == '':
                         if yes('Abort import? [yN]:'):
@@ -204,7 +204,7 @@ def import_paperkey(self, args):
                         print("only characters 0-9 and a-f and '-' are valid, try again")
                         continue
                     if sha256_truncated(idx.to_bytes(2, byteorder='big') + part, 2) != checksum:
-                        print('line checksum did not match, try line {0} again'.format(idx))
+                        print(f'line checksum did not match, try line {idx} again')
                         continue
                     result += part
                     if idx == lines:
diff --git a/src/borg/crypto/nonces.py b/src/borg/crypto/nonces.py
index fe5abc547..12a597484 100644
--- a/src/borg/crypto/nonces.py
+++ b/src/borg/crypto/nonces.py
@@ -22,7 +22,7 @@ def __init__(self, repository, manifest_nonce):
 
     def get_local_free_nonce(self):
         try:
-            with open(self.nonce_file, 'r') as fd:
+            with open(self.nonce_file) as fd:
                 return bytes_to_long(unhexlify(fd.read()))
         except FileNotFoundError:
             return None
diff --git a/src/borg/fuse.py b/src/borg/fuse.py
index 7cecdabe5..04183a008 100644
--- a/src/borg/fuse.py
+++ b/src/borg/fuse.py
@@ -234,7 +234,7 @@ def iter_archive_items(self, archive_item_ids, filter=None, consider_part_files=
         self.write_offset = write_offset
 
 
-class FuseBackend(object):
+class FuseBackend:
     """Virtual filesystem based on archive(s) to provide information to fuse
     """
 
diff --git a/src/borg/helpers/manifest.py b/src/borg/helpers/manifest.py
index 0703b4123..84871f736 100644
--- a/src/borg/helpers/manifest.py
+++ b/src/borg/helpers/manifest.py
@@ -233,7 +233,7 @@ def get_all_mandatory_features(self):
 
         for operation, requirements in feature_flags.items():
             if b'mandatory' in requirements:
-                result[operation.decode()] = set([feature.decode() for feature in requirements[b'mandatory']])
+                result[operation.decode()] = {feature.decode() for feature in requirements[b'mandatory']}
         return result
 
     def write(self):
diff --git a/src/borg/helpers/misc.py b/src/borg/helpers/misc.py
index bf7ae8065..96eb78993 100644
--- a/src/borg/helpers/misc.py
+++ b/src/borg/helpers/misc.py
@@ -91,13 +91,13 @@ def sysinfo():
     from ..fuse_impl import llfuse, BORG_FUSE_IMPL
     llfuse_name = llfuse.__name__ if llfuse else 'None'
     llfuse_version = (' %s' % llfuse.__version__) if llfuse else ''
-    llfuse_info = '%s%s [%s]' % (llfuse_name, llfuse_version, BORG_FUSE_IMPL)
+    llfuse_info = f'{llfuse_name}{llfuse_version} [{BORG_FUSE_IMPL}]'
     info = []
     if uname is not None:
-        info.append('Platform: %s' % (' '.join(uname), ))
+        info.append('Platform: {}'.format(' '.join(uname)))
     if linux_distribution is not None:
         info.append('Linux: %s %s %s' % linux_distribution)
-    info.append('Borg: %s  Python: %s %s msgpack: %s fuse: %s' % (
+    info.append('Borg: {}  Python: {} {} msgpack: {} fuse: {}'.format(
                 borg_version, python_implementation, python_version, msgpack_version, llfuse_info))
     info.append('PID: %d  CWD: %s' % (os.getpid(), os.getcwd()))
     info.append('sys.argv: %r' % sys.argv)
diff --git a/src/borg/helpers/parseformat.py b/src/borg/helpers/parseformat.py
index bc3359807..ebbc7b526 100644
--- a/src/borg/helpers/parseformat.py
+++ b/src/borg/helpers/parseformat.py
@@ -80,7 +80,7 @@ def interval(s):
         # range suffixes in ascending multiplier order
         ranges = [k for k, v in sorted(multiplier.items(), key=lambda t: t[1])]
         raise argparse.ArgumentTypeError(
-            'Unexpected interval time unit "%s": expected one of %r' % (s[-1], ranges))
+            f'Unexpected interval time unit "{s[-1]}": expected one of {ranges!r}')
 
     try:
         hours = int(number) * multiplier[suffix]
@@ -117,7 +117,7 @@ def ChunkerParams(s):
         return CHUNKER_PARAMS
     # this must stay last as it deals with old-style compat mode (no algorithm, 4 params, buzhash):
     if algo == CH_BUZHASH and count == 5 or count == 4:  # [buzhash, ]chunk_min, chunk_max, chunk_mask, window_size
-        chunk_min, chunk_max, chunk_mask, window_size = [int(p) for p in params[count - 4:]]
+        chunk_min, chunk_max, chunk_mask, window_size = (int(p) for p in params[count - 4:])
         if not (chunk_min <= chunk_mask <= chunk_max):
             raise ValueError('required: chunk_min <= chunk_mask <= chunk_max')
         if chunk_min < 6:
@@ -150,7 +150,7 @@ def partial_format(format, mapping):
     """
     for key, value in mapping.items():
         key = re.escape(key)
-        format = re.sub(r'(?<!\{)((\{%s\})|(\{%s:[^\}]*\}))' % (key, key),
+        format = re.sub(fr'(?<!\{{)((\{{{key}\}})|(\{{{key}:[^\}}]*\}}))',
                         lambda match: match.group(1).format_map(mapping),
                         format)
     return format
@@ -397,7 +397,7 @@ def parse(self, text, overrides={}):
         valid = self._parse(repo)
         self.archive = m.group('archive')
         self.raw = repo_raw if not self.archive else repo_raw + self.raw
-        self.processed = repo if not self.archive else '%s::%s' % (repo, self.archive)
+        self.processed = repo if not self.archive else f'{repo}::{self.archive}'
         return valid
 
     def _parse(self, text):
@@ -484,9 +484,9 @@ def canonical_path(self):
                 path = '/./' + self.path  # /./x = path x relative to cwd
             else:
                 path = self.path
-            return 'ssh://{}{}{}{}'.format('{}@'.format(self.user) if self.user else '',
+            return 'ssh://{}{}{}{}'.format(f'{self.user}@' if self.user else '',
                                            self._host,  # needed for ipv6 addrs
-                                           ':{}'.format(self.port) if self.port else '',
+                                           f':{self.port}' if self.port else '',
                                            path)
 
     def with_timestamp(self, timestamp):
@@ -947,7 +947,7 @@ def ellipsis_truncate(msg, space):
         # if there is very little space, just show ...
         return '...' + ' ' * (space - ellipsis_width)
     if space < ellipsis_width + msg_width:
-        return '%s...%s' % (swidth_slice(msg, space // 2 - ellipsis_width),
+        return '{}...{}'.format(swidth_slice(msg, space // 2 - ellipsis_width),
                             swidth_slice(msg, -space // 2))
     return msg + ' ' * (space - msg_width)
 
diff --git a/src/borg/helpers/process.py b/src/borg/helpers/process.py
index feac82c4d..bf87869f6 100644
--- a/src/borg/helpers/process.py
+++ b/src/borg/helpers/process.py
@@ -320,7 +320,7 @@ def create_filter_process(cmd, stream, stream_close, inbound=True):
             proc = popen_with_error_handling(cmd, stdin=subprocess.PIPE, stdout=filter_stream,
                                              log_prefix='filter-process: ', env=env)
         if not proc:
-            raise Error('filter %s: process creation failed' % (cmd, ))
+            raise Error(f'filter {cmd}: process creation failed')
         stream = proc.stdout if inbound else proc.stdin
         # inbound: do not close the pipe (this is the task of the filter process [== writer])
         # outbound: close the pipe, otherwise the filter process would not notice when we are done.
diff --git a/src/borg/helpers/time.py b/src/borg/helpers/time.py
index 39abffdc4..8b48076f7 100644
--- a/src/borg/helpers/time.py
+++ b/src/borg/helpers/time.py
@@ -131,7 +131,7 @@ def __format__(self, format_spec):
         return format_time(self.ts, format_spec=format_spec)
 
     def __str__(self):
-        return '{}'.format(self)
+        return f'{self}'
 
     def isoformat(self):
         return isoformat_time(self.ts)
diff --git a/src/borg/locking.py b/src/borg/locking.py
index c274abd83..ecd6d27ca 100644
--- a/src/borg/locking.py
+++ b/src/borg/locking.py
@@ -42,7 +42,7 @@ def __init__(self, timeout=None, sleep=None):
         self.end_time = None
 
     def __repr__(self):
-        return "<%s: start=%r end=%r timeout=%r sleep=%r>" % (
+        return "<{}: start={!r} end={!r} timeout={!r} sleep={!r}>".format(
             self.__class__.__name__, self.start_time, self.end_time,
             self.timeout_interval, self.sleep_interval)
 
@@ -118,7 +118,7 @@ def __exit__(self, *exc):
         self.release()
 
     def __repr__(self):
-        return "<%s: %r>" % (self.__class__.__name__, self.unique_name)
+        return f"<{self.__class__.__name__}: {self.unique_name!r}>"
 
     def acquire(self, timeout=None, sleep=None):
         if timeout is None:
@@ -299,7 +299,7 @@ def remove(self):
 
     def get(self, key):
         roster = self.load()
-        return set(tuple(e) for e in roster.get(key, []))
+        return {tuple(e) for e in roster.get(key, [])}
 
     def empty(self, *keys):
         return all(not self.get(key) for key in keys)
@@ -307,7 +307,7 @@ def empty(self, *keys):
     def modify(self, key, op):
         roster = self.load()
         try:
-            elements = set(tuple(e) for e in roster[key])
+            elements = {tuple(e) for e in roster[key]}
         except KeyError:
             elements = set()
         if op == ADD:
@@ -374,7 +374,7 @@ def __exit__(self, *exc):
         self.release()
 
     def __repr__(self):
-        return "<%s: %r>" % (self.__class__.__name__, self.id)
+        return f"<{self.__class__.__name__}: {self.id!r}>"
 
     def acquire(self, exclusive=None, remove=None, sleep=None):
         if exclusive is None:
diff --git a/src/borg/logger.py b/src/borg/logger.py
index 0fb7a062c..b24eb7711 100644
--- a/src/borg/logger.py
+++ b/src/borg/logger.py
@@ -46,7 +46,7 @@
 
 def _log_warning(message, category, filename, lineno, file=None, line=None):
     # for warnings, we just want to use the logging system, not stderr or other files
-    msg = "{0}:{1}: {2}: {3}".format(filename, lineno, category.__name__, message)
+    msg = f"{filename}:{lineno}: {category.__name__}: {message}"
     logger = create_logger(__name__)
     # Note: the warning will look like coming from here,
     # but msg contains info about where it really comes from
@@ -82,7 +82,7 @@ def setup_logging(stream=None, conf_fname=None, env_var='BORG_LOGGING_CONF', lev
             logger = logging.getLogger(__name__)
             borg_logger = logging.getLogger('borg')
             borg_logger.json = json
-            logger.debug('using logging configuration read from "{0}"'.format(conf_fname))
+            logger.debug(f'using logging configuration read from "{conf_fname}"')
             warnings.showwarning = _log_warning
             return None
         except Exception as err:  # XXX be more precise
@@ -110,7 +110,7 @@ def setup_logging(stream=None, conf_fname=None, env_var='BORG_LOGGING_CONF', lev
     configured = True
     logger = logging.getLogger(__name__)
     if err_msg:
-        logger.warning('setup_logging for "{0}" failed with "{1}".'.format(conf_fname, err_msg))
+        logger.warning(f'setup_logging for "{conf_fname}" failed with "{err_msg}".')
     logger.debug('using builtin fallback logging configuration')
     warnings.showwarning = _log_warning
     return handler
diff --git a/src/borg/patterns.py b/src/borg/patterns.py
index a3e34d401..49668ef2b 100644
--- a/src/borg/patterns.py
+++ b/src/borg/patterns.py
@@ -201,7 +201,7 @@ def match(self, path, normalize=True):
         return matches
 
     def __repr__(self):
-        return '%s(%s)' % (type(self), self.pattern)
+        return f'{type(self)}({self.pattern})'
 
     def __str__(self):
         return self.pattern_orig
@@ -315,7 +315,7 @@ def _match(self, path):
     ShellPattern,
 }
 
-_PATTERN_CLASS_BY_PREFIX = dict((i.PREFIX, i) for i in _PATTERN_CLASSES)
+_PATTERN_CLASS_BY_PREFIX = {i.PREFIX: i for i in _PATTERN_CLASSES}
 
 CmdTuple = namedtuple('CmdTuple', 'val cmd')
 
@@ -339,7 +339,7 @@ def get_pattern_class(prefix):
     try:
         return _PATTERN_CLASS_BY_PREFIX[prefix]
     except KeyError:
-        raise ValueError("Unknown pattern style: {}".format(prefix)) from None
+        raise ValueError(f"Unknown pattern style: {prefix}") from None
 
 
 def parse_pattern(pattern, fallback=FnmatchPattern, recurse_dir=True):
@@ -394,7 +394,7 @@ def parse_inclexcl_command(cmd_line_str, fallback=ShellPattern):
         try:
             val = get_pattern_class(remainder_str)
         except ValueError:
-            raise argparse.ArgumentTypeError("Invalid pattern style: {}".format(remainder_str))
+            raise argparse.ArgumentTypeError(f"Invalid pattern style: {remainder_str}")
     else:
         # determine recurse_dir based on command type
         recurse_dir = command_recurses_dir(cmd)
diff --git a/src/borg/platform/base.py b/src/borg/platform/base.py
index 6d90328e1..1eb929ee2 100644
--- a/src/borg/platform/base.py
+++ b/src/borg/platform/base.py
@@ -265,7 +265,7 @@ def getfqdn(name=''):
         name = socket.gethostname()
     try:
         addrs = socket.getaddrinfo(name, None, 0, socket.SOCK_DGRAM, 0, socket.AI_CANONNAME)
-    except socket.error:
+    except OSError:
         pass
     else:
         for addr in addrs:
@@ -288,7 +288,7 @@ def getfqdn(name=''):
 # thus, we offer BORG_HOST_ID where a user can set an own, unique id for each of his hosts.
 hostid = os.environ.get('BORG_HOST_ID')
 if not hostid:
-    hostid = '%s@%s' % (fqdn, uuid.getnode())
+    hostid = f'{fqdn}@{uuid.getnode()}'
 
 
 def get_process_id():
diff --git a/src/borg/remote.py b/src/borg/remote.py
index 77d395f5e..fa0772c60 100644
--- a/src/borg/remote.py
+++ b/src/borg/remote.py
@@ -286,7 +286,7 @@ def serve(self):
                                 else:
                                     tb_log_level = logging.ERROR
                                     msg = '%s Exception in RPC call' % e.__class__.__name__
-                                tb = '%s\n%s' % (traceback.format_exc(), sysinfo())
+                                tb = f'{traceback.format_exc()}\n{sysinfo()}'
                                 logging.error(msg)
                                 logging.log(tb_log_level, tb)
                             exc = 'Remote Exception (see remote log for the traceback)'
@@ -470,7 +470,7 @@ def do_rpc(self, *args, **kwargs):
                 if restriction.get('dontcare', False):
                     continue
 
-                raise self.RPCServerOutdated("{0} {1}={2!s}".format(f.__name__, name, named[name]),
+                raise self.RPCServerOutdated(f"{f.__name__} {name}={named[name]!s}",
                                              format_version(restriction['since']))
 
             return self.call(f.__name__, named, **extra)
@@ -622,7 +622,7 @@ def __del__(self):
             assert False, 'cleanup happened in Repository.__del__'
 
     def __repr__(self):
-        return '<%s %s>' % (self.__class__.__name__, self.location.canonical_path())
+        return f'<{self.__class__.__name__} {self.location.canonical_path()}>'
 
     def __enter__(self):
         return self
@@ -697,7 +697,7 @@ def ssh_cmd(self, location):
         if location.port:
             args += ['-p', str(location.port)]
         if location.user:
-            args.append('%s@%s' % (location.user, location.host))
+            args.append(f'{location.user}@{location.host}')
         else:
             args.append('%s' % location.host)
         return args
@@ -941,8 +941,7 @@ def get(self, id):
             return resp
 
     def get_many(self, ids, is_preloaded=False):
-        for resp in self.call_many('get', [{'id': id} for id in ids], is_preloaded=is_preloaded):
-            yield resp
+        yield from self.call_many('get', [{'id': id} for id in ids], is_preloaded=is_preloaded)
 
     @api(since=parse_version('1.0.0'))
     def put(self, id, data, wait=True):
diff --git a/src/borg/repository.py b/src/borg/repository.py
index f9a2c11f6..bb67c5a3f 100644
--- a/src/borg/repository.py
+++ b/src/borg/repository.py
@@ -190,7 +190,7 @@ def __del__(self):
             assert False, "cleanup happened in Repository.__del__"
 
     def __repr__(self):
-        return '<%s %s>' % (self.__class__.__name__, self.path)
+        return f'<{self.__class__.__name__} {self.path}>'
 
     def __enter__(self):
         if self.do_create:
@@ -347,7 +347,7 @@ def get_free_nonce(self):
 
         nonce_path = os.path.join(self.path, 'nonce')
         try:
-            with open(nonce_path, 'r') as fd:
+            with open(nonce_path) as fd:
                 return int.from_bytes(unhexlify(fd.read()), byteorder='big')
         except FileNotFoundError:
             return None
@@ -716,7 +716,7 @@ def check_free_space(self):
         except OSError as os_error:
             logger.warning('Failed to check free space before committing: ' + str(os_error))
             return
-        logger.debug('check_free_space: required bytes {}, free bytes {}'.format(required_free_space, free_space))
+        logger.debug(f'check_free_space: required bytes {required_free_space}, free bytes {free_space}')
         if free_space < required_free_space:
             if self.created:
                 logger.error('Not enough free space to initialize repository at this location.')
@@ -924,7 +924,7 @@ def _update_index(self, segment, objects, report=None):
             elif tag == TAG_COMMIT:
                 continue
             else:
-                msg = 'Unexpected tag {} in segment {}'.format(tag, segment)
+                msg = f'Unexpected tag {tag} in segment {segment}'
                 if report is None:
                     raise self.CheckNeeded(msg)
                 else:
@@ -1045,7 +1045,7 @@ def report_error(msg):
         # self.index, self.segments, self.compact now reflect the state of the segment files up to <transaction_id>
         # We might need to add a commit tag if no committed segment is found
         if repair and segments_transaction_id is None:
-            report_error('Adding commit tag to segment {}'.format(transaction_id))
+            report_error(f'Adding commit tag to segment {transaction_id}')
             self.io.segment = transaction_id + 1
             self.io.write_commit()
         if not partial:
@@ -1484,7 +1484,7 @@ def iter_objects(self, segment, offset=0, include_data=False, read_data=True):
             # Repository.scan() calls us with segment > 0 when it continues an ongoing iteration
             # from a marker position - but then we have checked the magic before already.
             if fd.read(MAGIC_LEN) != MAGIC:
-                raise IntegrityError('Invalid segment magic [segment {}, offset {}]'.format(segment, 0))
+                raise IntegrityError(f'Invalid segment magic [segment {segment}, offset {0}]')
             offset = MAGIC_LEN
         header = fd.read(self.header_fmt.size)
         while header:
@@ -1613,7 +1613,7 @@ def write_put(self, id, data, raise_full=False):
         data_size = len(data)
         if data_size > MAX_DATA_SIZE:
             # this would push the segment entry size beyond MAX_OBJECT_SIZE.
-            raise IntegrityError('More than allowed put data [{} > {}]'.format(data_size, MAX_DATA_SIZE))
+            raise IntegrityError(f'More than allowed put data [{data_size} > {MAX_DATA_SIZE}]')
         fd = self.get_write_fd(want_new=(id == Manifest.MANIFEST_ID), raise_full=raise_full)
         size = data_size + self.put_header_fmt.size
         offset = self.offset
diff --git a/src/borg/shellpattern.py b/src/borg/shellpattern.py
index 899544975..c9447704b 100644
--- a/src/borg/shellpattern.py
+++ b/src/borg/shellpattern.py
@@ -33,7 +33,7 @@ def translate(pat, match_end=r"\Z"):
             if i + 1 < n and pat[i] == "*" and pat[i + 1] == sep:
                 # **/ == wildcard for 0+ full (relative) directory names with trailing slashes; the forward slash stands
                 # for the platform-specific path separator
-                res += r"(?:[^\%s]*\%s)*" % (sep, sep)
+                res += fr"(?:[^\{sep}]*\{sep})*"
                 i += 2
             else:
                 # * == wildcard for name parts (does not cross path separator)
diff --git a/src/borg/testsuite/__init__.py b/src/borg/testsuite/__init__.py
index aa7b3e882..b1db8aa95 100644
--- a/src/borg/testsuite/__init__.py
+++ b/src/borg/testsuite/__init__.py
@@ -58,7 +58,7 @@ def unopened_tempfile():
         yield os.path.join(tempdir, "file")
 
 
-@functools.lru_cache()
+@functools.lru_cache
 def are_symlinks_supported():
     with unopened_tempfile() as filepath:
         try:
@@ -70,7 +70,7 @@ def are_symlinks_supported():
     return False
 
 
-@functools.lru_cache()
+@functools.lru_cache
 def are_hardlinks_supported():
     if not hasattr(os, 'link'):
         # some pythons do not have os.link
@@ -89,7 +89,7 @@ def are_hardlinks_supported():
     return False
 
 
-@functools.lru_cache()
+@functools.lru_cache
 def are_fifos_supported():
     with unopened_tempfile() as filepath:
         try:
@@ -104,7 +104,7 @@ def are_fifos_supported():
         return False
 
 
-@functools.lru_cache()
+@functools.lru_cache
 def is_utime_fully_supported():
     with unopened_tempfile() as filepath:
         # Some filesystems (such as SSHFS) don't support utime on symlinks
@@ -124,7 +124,7 @@ def is_utime_fully_supported():
         return False
 
 
-@functools.lru_cache()
+@functools.lru_cache
 def is_birthtime_fully_supported():
     if not hasattr(os.stat_result, 'st_birthtime'):
         return False
@@ -172,9 +172,9 @@ class BaseTestCase(unittest.TestCase):
 
     @contextmanager
     def assert_creates_file(self, path):
-        assert not os.path.exists(path), '{} should not exist'.format(path)
+        assert not os.path.exists(path), f'{path} should not exist'
         yield
-        assert os.path.exists(path), '{} should exist'.format(path)
+        assert os.path.exists(path), f'{path} should exist'
 
     def assert_dirs_equal(self, dir1, dir2, **kwargs):
         diff = filecmp.dircmp(dir1, dir2)
@@ -293,7 +293,7 @@ def wait_for_mountstate(self, mountpoint, *, mounted, timeout=5):
             if os.path.ismount(mountpoint) == mounted:
                 return
             time.sleep(0.1)
-        message = 'Waiting for %s of %s' % ('mount' if mounted else 'umount', mountpoint)
+        message = 'Waiting for {} of {}'.format('mount' if mounted else 'umount', mountpoint)
         raise TimeoutError(message)
 
     @contextmanager
diff --git a/src/borg/testsuite/archive.py b/src/borg/testsuite/archive.py
index 934d76b61..db9ed573b 100644
--- a/src/borg/testsuite/archive.py
+++ b/src/borg/testsuite/archive.py
@@ -55,10 +55,10 @@ def tests_stats_progress(stats, monkeypatch, columns=80):
 def test_stats_format(stats):
     assert str(stats) == """\
 This archive:                   20 B                 10 B                 10 B"""
-    s = "{0.osize_fmt}".format(stats)
+    s = f"{stats.osize_fmt}"
     assert s == "20 B"
     # kind of redundant, but id is variable so we can't match reliably
-    assert repr(stats) == '<Statistics object at {:#x} (20, 10, 10)>'.format(id(stats))
+    assert repr(stats) == f'<Statistics object at {id(stats):#x} (20, 10, 10)>'
 
 
 class MockCache:
diff --git a/src/borg/testsuite/archiver.py b/src/borg/testsuite/archiver.py
index 11d83525d..58b760be3 100644
--- a/src/borg/testsuite/archiver.py
+++ b/src/borg/testsuite/archiver.py
@@ -1867,7 +1867,7 @@ def test_unknown_mandatory_feature_in_cache(self):
             manifest, key = Manifest.load(repository, Manifest.NO_OPERATION_CHECK)
             with Cache(repository, key, manifest) as cache:
                 cache.begin_txn()
-                cache.cache_config.mandatory_features = set(['unknown-feature'])
+                cache.cache_config.mandatory_features = {'unknown-feature'}
                 cache.commit()
 
         if self.FORK_DEFAULT:
@@ -1891,7 +1891,7 @@ def wipe_wrapper(*args):
                 repository._location = Location(self.repository_location)
             manifest, key = Manifest.load(repository, Manifest.NO_OPERATION_CHECK)
             with Cache(repository, key, manifest) as cache:
-                assert cache.cache_config.mandatory_features == set([])
+                assert cache.cache_config.mandatory_features == set()
 
     def test_progress_on(self):
         self.create_regular_file('file1', size=1024 * 80)
@@ -2748,7 +2748,7 @@ def wrapper(self, old_id, new_id):
                 pass
             with open(assert_data_file, 'rb') as _in:
                 assert_data = pickle.load(_in)
-            print('\nLock.migrate_lock(): assert_data = %r.' % (assert_data, ), file=sys.stderr, flush=True)
+            print(f'\nLock.migrate_lock(): assert_data = {assert_data!r}.', file=sys.stderr, flush=True)
             exception = assert_data['exception']
             if exception is not None:
                 extracted_tb = assert_data['exception.extr_tb']
@@ -3089,14 +3089,14 @@ def test_key_export_keyfile(self):
         repo_id = self._extract_repository_id(self.repository_path)
         self.cmd('key', 'export', self.repository_location, export_file)
 
-        with open(export_file, 'r') as fd:
+        with open(export_file) as fd:
             export_contents = fd.read()
 
         assert export_contents.startswith('BORG_KEY ' + bin_to_hex(repo_id) + '\n')
 
         key_file = self.keys_path + '/' + os.listdir(self.keys_path)[0]
 
-        with open(key_file, 'r') as fd:
+        with open(key_file) as fd:
             key_contents = fd.read()
 
         assert key_contents == export_contents
@@ -3105,7 +3105,7 @@ def test_key_export_keyfile(self):
 
         self.cmd('key', 'import', self.repository_location, export_file)
 
-        with open(key_file, 'r') as fd:
+        with open(key_file) as fd:
             key_contents2 = fd.read()
 
         assert key_contents2 == key_contents
@@ -3117,7 +3117,7 @@ def test_key_import_keyfile_with_borg_key_file(self):
         self.cmd('key', 'export', self.repository_location, exported_key_file)
 
         key_file = os.path.join(self.keys_path, os.listdir(self.keys_path)[0])
-        with open(key_file, 'r') as fd:
+        with open(key_file) as fd:
             key_contents = fd.read()
         os.unlink(key_file)
 
@@ -3126,7 +3126,7 @@ def test_key_import_keyfile_with_borg_key_file(self):
             self.cmd('key', 'import', self.repository_location, exported_key_file)
         assert not os.path.isfile(key_file), '"borg key import" should respect BORG_KEY_FILE'
 
-        with open(imported_key_file, 'r') as fd:
+        with open(imported_key_file) as fd:
             imported_key_contents = fd.read()
         assert imported_key_contents == key_contents
 
@@ -3136,7 +3136,7 @@ def test_key_export_repokey(self):
         repo_id = self._extract_repository_id(self.repository_path)
         self.cmd('key', 'export', self.repository_location, export_file)
 
-        with open(export_file, 'r') as fd:
+        with open(export_file) as fd:
             export_contents = fd.read()
 
         assert export_contents.startswith('BORG_KEY ' + bin_to_hex(repo_id) + '\n')
@@ -3167,7 +3167,7 @@ def test_key_export_qr(self):
         repo_id = self._extract_repository_id(self.repository_path)
         self.cmd('key', 'export', '--qr-html', self.repository_location, export_file)
 
-        with open(export_file, 'r', encoding='utf-8') as fd:
+        with open(export_file, encoding='utf-8') as fd:
             export_contents = fd.read()
 
         assert bin_to_hex(repo_id) in export_contents
@@ -3221,7 +3221,7 @@ def test_key_export_paperkey(self):
 
         self.cmd('key', 'export', '--paper', self.repository_location, export_file)
 
-        with open(export_file, 'r') as fd:
+        with open(export_file) as fd:
             export_contents = fd.read()
 
         assert export_contents == """To restore key use borg key import --paper /path/to/repo
@@ -3284,7 +3284,7 @@ def test_debug_dump_manifest(self):
         dump_file = self.output_path + '/dump'
         output = self.cmd('debug', 'dump-manifest', self.repository_location, dump_file)
         assert output == ""
-        with open(dump_file, "r") as f:
+        with open(dump_file) as f:
             result = json.load(f)
         assert 'archives' in result
         assert 'config' in result
@@ -3299,7 +3299,7 @@ def test_debug_dump_archive(self):
         dump_file = self.output_path + '/dump'
         output = self.cmd('debug', 'dump-archive', self.repository_location + "::test", dump_file)
         assert output == ""
-        with open(dump_file, "r") as f:
+        with open(dump_file) as f:
             result = json.load(f)
         assert '_name' in result
         assert '_manifest_entry' in result
@@ -4144,7 +4144,7 @@ def do_asserts(output, can_compare_ids):
             # File contents changed (deleted and replaced with a new file)
             change = 'B' if can_compare_ids else '{:<19}'.format('modified')
             assert 'file_replaced' in output  # added to debug #3494
-            assert '{} input/file_replaced'.format(change) in output
+            assert f'{change} input/file_replaced' in output
 
             # File unchanged
             assert 'input/file_unchanged' not in output
@@ -4174,9 +4174,9 @@ def do_asserts(output, can_compare_ids):
             # should notice the changes in both links. However, the symlink
             # pointing to the file is not changed.
             change = '0 B' if can_compare_ids else '{:<19}'.format('modified')
-            assert '{} input/empty'.format(change) in output
+            assert f'{change} input/empty' in output
             if are_hardlinks_supported():
-                assert '{} input/hardlink_contents_changed'.format(change) in output
+                assert f'{change} input/hardlink_contents_changed' in output
             if are_symlinks_supported():
                 assert 'input/link_target_contents_changed' not in output
 
diff --git a/src/borg/testsuite/compress.py b/src/borg/testsuite/compress.py
index 0c284e144..3942c3537 100644
--- a/src/borg/testsuite/compress.py
+++ b/src/borg/testsuite/compress.py
@@ -147,7 +147,7 @@ def test_obfuscate():
     # 2 id bytes compression, 2 id bytes obfuscator. 4 length bytes
     assert len(data) + 8 <= len(compressed) <= len(data) * 101 + 8
     # compressing 100 times the same data should give at least 50 different result sizes
-    assert len(set(len(compressor.compress(data)) for i in range(100))) > 50
+    assert len({len(compressor.compress(data)) for i in range(100)}) > 50
 
     cs = CompressionSpec('obfuscate,2,lz4')
     assert isinstance(cs.inner.compressor, LZ4)
@@ -158,7 +158,7 @@ def test_obfuscate():
     min_compress, max_compress = 0.2, 0.001  # estimate compression factor outer boundaries
     assert max_compress * len(data) + 8 <= len(compressed) <= min_compress * len(data) * 1001 + 8
     # compressing 100 times the same data should give multiple different result sizes
-    assert len(set(len(compressor.compress(data)) for i in range(100))) > 10
+    assert len({len(compressor.compress(data)) for i in range(100)}) > 10
 
     cs = CompressionSpec('obfuscate,6,zstd,3')
     assert isinstance(cs.inner.compressor, ZSTD)
@@ -169,7 +169,7 @@ def test_obfuscate():
     min_compress, max_compress = 0.2, 0.001  # estimate compression factor outer boundaries
     assert max_compress * len(data) + 8 <= len(compressed) <= min_compress * len(data) * 10000001 + 8
     # compressing 100 times the same data should give multiple different result sizes
-    assert len(set(len(compressor.compress(data)) for i in range(100))) > 90
+    assert len({len(compressor.compress(data)) for i in range(100)}) > 90
 
     cs = CompressionSpec('obfuscate,2,auto,zstd,10')
     assert isinstance(cs.inner.compressor, Auto)
@@ -180,7 +180,7 @@ def test_obfuscate():
     min_compress, max_compress = 0.2, 0.001  # estimate compression factor outer boundaries
     assert max_compress * len(data) + 8 <= len(compressed) <= min_compress * len(data) * 1001 + 8
     # compressing 100 times the same data should give multiple different result sizes
-    assert len(set(len(compressor.compress(data)) for i in range(100))) > 10
+    assert len({len(compressor.compress(data)) for i in range(100)}) > 10
 
     cs = CompressionSpec('obfuscate,110,none')
     assert isinstance(cs.inner.compressor, CNONE)
diff --git a/src/borg/testsuite/file_integrity.py b/src/borg/testsuite/file_integrity.py
index 6dee247a1..af50f15c0 100644
--- a/src/borg/testsuite/file_integrity.py
+++ b/src/borg/testsuite/file_integrity.py
@@ -1,4 +1,3 @@
-
 import pytest
 
 from ..crypto.file_integrity import IntegrityCheckedFile, DetachedIntegrityCheckedFile, FileIntegrityError
diff --git a/src/borg/testsuite/helpers.py b/src/borg/testsuite/helpers.py
index 2e30e36be..5a5df302e 100644
--- a/src/borg/testsuite/helpers.py
+++ b/src/borg/testsuite/helpers.py
@@ -225,7 +225,7 @@ def test_format_path(self, monkeypatch):
         monkeypatch.delenv('BORG_REPO', raising=False)
         test_pid = os.getpid()
         assert repr(Location('/some/path::archive{pid}')) == \
-            "Location(proto='file', user=None, host=None, port=None, path='/some/path', archive='archive{}')".format(test_pid)
+            f"Location(proto='file', user=None, host=None, port=None, path='/some/path', archive='archive{test_pid}')"
         location_time1 = Location('/some/path::archive{now:%s}')
         sleep(1.1)
         location_time2 = Location('/some/path::archive{now:%s}')
@@ -259,11 +259,11 @@ def test_ssh_placeholder(self, monkeypatch):
         from borg.platform import hostname
         monkeypatch.setenv('BORG_REPO', 'ssh://user@host:1234/{hostname}')
         assert repr(Location('::archive')) == \
-            "Location(proto='ssh', user='user', host='host', port=1234, path='/{}', archive='archive')".format(hostname)
+            f"Location(proto='ssh', user='user', host='host', port=1234, path='/{hostname}', archive='archive')"
         assert repr(Location('::')) == \
-            "Location(proto='ssh', user='user', host='host', port=1234, path='/{}', archive=None)".format(hostname)
+            f"Location(proto='ssh', user='user', host='host', port=1234, path='/{hostname}', archive=None)"
         assert repr(Location()) == \
-            "Location(proto='ssh', user='user', host='host', port=1234, path='/{}', archive=None)".format(hostname)
+            f"Location(proto='ssh', user='user', host='host', port=1234, path='/{hostname}', archive=None)"
 
     def test_file(self, monkeypatch):
         monkeypatch.setenv('BORG_REPO', 'file:///some/path')
@@ -380,7 +380,7 @@ def __init__(self, ts, id):
         self.id = id
 
     def __repr__(self):
-        return "{0}: {1}".format(self.id, self.ts.isoformat())
+        return f"{self.id}: {self.ts.isoformat()}"
 
 
 @pytest.mark.parametrize(
diff --git a/src/borg/testsuite/lrucache.py b/src/borg/testsuite/lrucache.py
index eea171d64..6d1ab4adf 100644
--- a/src/borg/testsuite/lrucache.py
+++ b/src/borg/testsuite/lrucache.py
@@ -14,7 +14,7 @@ def test_lrucache(self):
         for i, x in enumerate('abc'):
             c[x] = i
         assert len(c) == 2
-        assert c.items() == set([('b', 1), ('c', 2)])
+        assert c.items() == {('b', 1), ('c', 2)}
         assert 'a' not in c
         assert 'b' in c
         with pytest.raises(KeyError):
diff --git a/src/borg/testsuite/nanorst.py b/src/borg/testsuite/nanorst.py
index 065436094..b25336b62 100644
--- a/src/borg/testsuite/nanorst.py
+++ b/src/borg/testsuite/nanorst.py
@@ -1,4 +1,3 @@
-
 import pytest
 
 from ..nanorst import rst_to_text
diff --git a/src/borg/testsuite/nonces.py b/src/borg/testsuite/nonces.py
index d0bc85eaf..6d6701631 100644
--- a/src/borg/testsuite/nonces.py
+++ b/src/borg/testsuite/nonces.py
@@ -37,7 +37,7 @@ def setUp(self):
         self.repository = None
 
     def cache_nonce(self):
-        with open(os.path.join(get_security_dir(self.repository.id_str), 'nonce'), "r") as fd:
+        with open(os.path.join(get_security_dir(self.repository.id_str), 'nonce')) as fd:
             return fd.read()
 
     def set_cache_nonce(self, nonce):
diff --git a/src/borg/testsuite/patterns.py b/src/borg/testsuite/patterns.py
index 543ef7bb1..e26ead1e8 100644
--- a/src/borg/testsuite/patterns.py
+++ b/src/borg/testsuite/patterns.py
@@ -204,7 +204,7 @@ def use_normalized_unicode():
 def _make_test_patterns(pattern):
     return [PathPrefixPattern(pattern),
             FnmatchPattern(pattern),
-            RegexPattern("^{}/foo$".format(pattern)),
+            RegexPattern(f"^{pattern}/foo$"),
             ShellPattern(pattern),
             ]
 
@@ -275,7 +275,7 @@ def test_exclude_patterns_from_file(tmpdir, lines, expected):
 
     def evaluate(filename):
         patterns = []
-        load_exclude_file(open(filename, "rt"), patterns)
+        load_exclude_file(open(filename), patterns)
         matcher = PatternMatcher(fallback=True)
         matcher.add_inclexcl(patterns)
         return [path for path in files if matcher.match(path)]
@@ -306,7 +306,7 @@ def test_load_patterns_from_file(tmpdir, lines, expected_roots, expected_numpatt
     def evaluate(filename):
         roots = []
         inclexclpatterns = []
-        load_pattern_file(open(filename, "rt"), roots, inclexclpatterns)
+        load_pattern_file(open(filename), roots, inclexclpatterns)
         return roots, len(inclexclpatterns)
     patternfile = tmpdir.join("patterns.txt")
 
@@ -356,7 +356,7 @@ def test_load_invalid_patterns_from_file(tmpdir, lines):
     with pytest.raises(argparse.ArgumentTypeError):
         roots = []
         inclexclpatterns = []
-        load_pattern_file(open(filename, "rt"), roots, inclexclpatterns)
+        load_pattern_file(open(filename), roots, inclexclpatterns)
 
 
 @pytest.mark.parametrize("lines, expected", [
@@ -400,7 +400,7 @@ def evaluate(filename):
         matcher = PatternMatcher(fallback=True)
         roots = []
         inclexclpatterns = []
-        load_pattern_file(open(filename, "rt"), roots, inclexclpatterns)
+        load_pattern_file(open(filename), roots, inclexclpatterns)
         matcher.add_inclexcl(inclexclpatterns)
         return [path for path in files if matcher.match(path)]
 
diff --git a/src/borg/testsuite/platform.py b/src/borg/testsuite/platform.py
index d0b510db8..659e4376e 100644
--- a/src/borg/testsuite/platform.py
+++ b/src/borg/testsuite/platform.py
@@ -53,7 +53,7 @@ def user_exists(username):
     return False
 
 
-@functools.lru_cache()
+@functools.lru_cache
 def are_acls_working():
     with unopened_tempfile() as filepath:
         open(filepath, 'w').close()
@@ -118,12 +118,12 @@ def test_non_ascii_acl(self):
         # but in practice they seem to be out there and must not make our code explode.
         file = tempfile.NamedTemporaryFile()
         self.assert_equal(self.get_acl(file.name), {})
-        nothing_special = 'user::rw-\ngroup::r--\nmask::rw-\nother::---\n'.encode('ascii')
+        nothing_special = b'user::rw-\ngroup::r--\nmask::rw-\nother::---\n'
         # TODO: can this be tested without having an existing system user übel with uid 666 gid 666?
-        user_entry = 'user:übel:rw-:666'.encode('utf-8')
-        user_entry_numeric = 'user:666:rw-:666'.encode('ascii')
-        group_entry = 'group:übel:rw-:666'.encode('utf-8')
-        group_entry_numeric = 'group:666:rw-:666'.encode('ascii')
+        user_entry = 'user:übel:rw-:666'.encode()
+        user_entry_numeric = b'user:666:rw-:666'
+        group_entry = 'group:übel:rw-:666'.encode()
+        group_entry_numeric = b'group:666:rw-:666'
         acl = b'\n'.join([nothing_special, user_entry, group_entry])
         self.set_acl(file.name, access=acl, numeric_ids=False)
         acl_access = self.get_acl(file.name, numeric_ids=False)['acl_access']
diff --git a/src/borg/testsuite/repository.py b/src/borg/testsuite/repository.py
index 580f52e2e..c52820e33 100644
--- a/src/borg/testsuite/repository.py
+++ b/src/borg/testsuite/repository.py
@@ -528,14 +528,14 @@ def test_commit_nonce_reservation(self):
                 self.repository.commit_nonce_reservation(0x200, 15)
 
             self.repository.commit_nonce_reservation(0x200, None)
-            with open(os.path.join(self.repository.path, "nonce"), "r") as fd:
+            with open(os.path.join(self.repository.path, "nonce")) as fd:
                 assert fd.read() == "0000000000000200"
 
             with pytest.raises(Exception):
                 self.repository.commit_nonce_reservation(0x200, 15)
 
             self.repository.commit_nonce_reservation(0x400, 0x200)
-            with open(os.path.join(self.repository.path, "nonce"), "r") as fd:
+            with open(os.path.join(self.repository.path, "nonce")) as fd:
                 assert fd.read() == "0000000000000400"
 
 
@@ -710,7 +710,7 @@ def get_head(self):
         return sorted(int(n) for n in os.listdir(os.path.join(self.tmppath, 'repository', 'data', '0')) if n.isdigit())[-1]
 
     def open_index(self):
-        return NSIndex.read(os.path.join(self.tmppath, 'repository', 'index.{}'.format(self.get_head())))
+        return NSIndex.read(os.path.join(self.tmppath, 'repository', f'index.{self.get_head()}'))
 
     def corrupt_object(self, id_):
         idx = self.open_index()
@@ -723,18 +723,18 @@ def delete_segment(self, segment):
         os.unlink(os.path.join(self.tmppath, 'repository', 'data', '0', str(segment)))
 
     def delete_index(self):
-        os.unlink(os.path.join(self.tmppath, 'repository', 'index.{}'.format(self.get_head())))
+        os.unlink(os.path.join(self.tmppath, 'repository', f'index.{self.get_head()}'))
 
     def rename_index(self, new_name):
-        os.rename(os.path.join(self.tmppath, 'repository', 'index.{}'.format(self.get_head())),
+        os.rename(os.path.join(self.tmppath, 'repository', f'index.{self.get_head()}'),
                   os.path.join(self.tmppath, 'repository', new_name))
 
     def list_objects(self):
-        return set(int(key) for key in self.repository.list())
+        return {int(key) for key in self.repository.list()}
 
     def test_repair_corrupted_segment(self):
         self.add_objects([[1, 2, 3], [4, 5], [6]])
-        self.assert_equal(set([1, 2, 3, 4, 5, 6]), self.list_objects())
+        self.assert_equal({1, 2, 3, 4, 5, 6}, self.list_objects())
         self.check(status=True)
         self.corrupt_object(5)
         self.assert_raises(IntegrityError, lambda: self.get_objects(5))
@@ -746,22 +746,22 @@ def test_repair_corrupted_segment(self):
         self.check(repair=True, status=True)
         self.get_objects(4)
         self.check(status=True)
-        self.assert_equal(set([1, 2, 3, 4, 6]), self.list_objects())
+        self.assert_equal({1, 2, 3, 4, 6}, self.list_objects())
 
     def test_repair_missing_segment(self):
         self.add_objects([[1, 2, 3], [4, 5, 6]])
-        self.assert_equal(set([1, 2, 3, 4, 5, 6]), self.list_objects())
+        self.assert_equal({1, 2, 3, 4, 5, 6}, self.list_objects())
         self.check(status=True)
         self.delete_segment(2)
         self.repository.rollback()
         self.check(repair=True, status=True)
-        self.assert_equal(set([1, 2, 3]), self.list_objects())
+        self.assert_equal({1, 2, 3}, self.list_objects())
 
     def test_repair_missing_commit_segment(self):
         self.add_objects([[1, 2, 3], [4, 5, 6]])
         self.delete_segment(3)
         self.assert_raises(Repository.ObjectNotFound, lambda: self.get_objects(4))
-        self.assert_equal(set([1, 2, 3]), self.list_objects())
+        self.assert_equal({1, 2, 3}, self.list_objects())
 
     def test_repair_corrupted_commit_segment(self):
         self.add_objects([[1, 2, 3], [4, 5, 6]])
@@ -771,7 +771,7 @@ def test_repair_corrupted_commit_segment(self):
         self.assert_raises(Repository.ObjectNotFound, lambda: self.get_objects(4))
         self.check(status=True)
         self.get_objects(3)
-        self.assert_equal(set([1, 2, 3]), self.list_objects())
+        self.assert_equal({1, 2, 3}, self.list_objects())
 
     def test_repair_no_commits(self):
         self.add_objects([[1, 2, 3]])
@@ -786,14 +786,14 @@ def test_repair_no_commits(self):
         self.assert_equal(self.list_indices(), ['index.2'])
         self.check(status=True)
         self.get_objects(3)
-        self.assert_equal(set([1, 2, 3]), self.list_objects())
+        self.assert_equal({1, 2, 3}, self.list_objects())
 
     def test_repair_missing_index(self):
         self.add_objects([[1, 2, 3], [4, 5, 6]])
         self.delete_index()
         self.check(status=True)
         self.get_objects(4)
-        self.assert_equal(set([1, 2, 3, 4, 5, 6]), self.list_objects())
+        self.assert_equal({1, 2, 3, 4, 5, 6}, self.list_objects())
 
     def test_repair_index_too_new(self):
         self.add_objects([[1, 2, 3], [4, 5, 6]])
@@ -802,7 +802,7 @@ def test_repair_index_too_new(self):
         self.check(status=True)
         self.assert_equal(self.list_indices(), ['index.3'])
         self.get_objects(4)
-        self.assert_equal(set([1, 2, 3, 4, 5, 6]), self.list_objects())
+        self.assert_equal({1, 2, 3, 4, 5, 6}, self.list_objects())
 
     def test_crash_before_compact(self):
         self.repository.put(H(0), b'data')
diff --git a/src/borg/testsuite/upgrader.py b/src/borg/testsuite/upgrader.py
index 9e6cd6ab0..ff921e4b7 100644
--- a/src/borg/testsuite/upgrader.py
+++ b/src/borg/testsuite/upgrader.py
@@ -54,7 +54,7 @@ def key_valid(path):
     """
     keyfile = os.path.join(get_keys_dir(),
                            os.path.basename(path))
-    with open(keyfile, 'r') as f:
+    with open(keyfile) as f:
         return f.read().startswith(KeyfileKey.FILE_ID)
 
 
diff --git a/src/borg/upgrader.py b/src/borg/upgrader.py
index fc0851f32..5be0aac0e 100644
--- a/src/borg/upgrader.py
+++ b/src/borg/upgrader.py
@@ -36,7 +36,7 @@ def upgrade(self, dryrun=True, inplace=False, progress=False):
         with self:
             backup = None
             if not inplace:
-                backup = '{}.before-upgrade-{:%Y-%m-%d-%H:%M:%S}'.format(self.path, datetime.datetime.now())
+                backup = f'{self.path}.before-upgrade-{datetime.datetime.now():%Y-%m-%d-%H:%M:%S}'
                 logger.info('making a hardlink copy in %s', backup)
                 if not dryrun:
                     shutil.copytree(self.path, backup, copy_function=os.link)
@@ -144,7 +144,7 @@ def convert_keyfiles(keyfile, dryrun):
         problem because the keyfiles are small (compared to, say,
         all the segments)."""
         logger.info("converting keyfile %s" % keyfile)
-        with open(keyfile, 'r') as f:
+        with open(keyfile) as f:
             data = f.read()
         data = data.replace(AtticKeyfileKey.FILE_ID, KeyfileKey.FILE_ID, 1)
         keyfile = os.path.join(get_keys_dir(), os.path.basename(keyfile))
@@ -214,12 +214,12 @@ def copy_cache_file(path):
                 if os.path.exists(borg_file):
                     logger.warning("borg cache file already exists in %s, not copying from Attic", borg_file)
                 else:
-                    logger.info("copying attic cache file from %s to %s" % (attic_file, borg_file))
+                    logger.info(f"copying attic cache file from {attic_file} to {borg_file}")
                     if not dryrun:
                         shutil.copyfile(attic_file, borg_file)
                 return borg_file
             else:
-                logger.warning("no %s cache file found in %s" % (path, attic_file))
+                logger.warning(f"no {path} cache file found in {attic_file}")
                 return None
 
         # XXX: untested, because generating cache files is a PITA, see
@@ -270,7 +270,7 @@ def find_key_file(cls, repository):
             raise KeyfileNotFoundError(repository.path, keys_dir)
         for name in os.listdir(keys_dir):
             filename = os.path.join(keys_dir, name)
-            with open(filename, 'r') as fd:
+            with open(filename) as fd:
                 line = fd.readline().strip()
                 if line and line.startswith(cls.FILE_ID) and line[10:] == repository.id_str:
                     return filename
@@ -319,7 +319,7 @@ def find_key_file(cls, repository):
             raise KeyfileNotFoundError(repository.path, keys_dir)
         for name in os.listdir(keys_dir):
             filename = os.path.join(keys_dir, name)
-            with open(filename, 'r') as fd:
+            with open(filename) as fd:
                 line = fd.readline().strip()
                 if line and line.startswith(cls.FILE_ID) and line[len(cls.FILE_ID) + 1:] == repository.id_str:
                     return filename
diff --git a/src/borg/xattr.py b/src/borg/xattr.py
index d34339370..8a731340c 100644
--- a/src/borg/xattr.py
+++ b/src/borg/xattr.py
@@ -91,7 +91,7 @@ def get_all(path, follow_symlinks=False):
                     pass
                 elif e.errno == errno.EPERM:
                     # we were not permitted to read this attribute, still can continue trying to read others
-                    logger.warning('%s: Operation not permitted when reading extended attribute %s' % (
+                    logger.warning('{}: Operation not permitted when reading extended attribute {}'.format(
                                    path_str, name_str))
                 else:
                     raise