replace usages of fromisoformat() with strptime()

fromisoformat was only introduced with Python 3.7 while we
still support Python 3.5.

Fixes #2292.

nominatim/db/status.py

@@ -9,6 +9,7 @@ from nominatim.tools.exec_utils import get_url
 from nominatim.errors import UsageError
 
 LOG = logging.getLogger()
+ISODATE_FORMAT = '%Y-%m-%dT%H:%M:%S'
 
 def compute_database_date(conn):
     """ Determine the date of the database from the newest object in the
@@ -36,7 +37,7 @@ def compute_database_date(conn):
 
     LOG.debug("Found timestamp %s", match[1])
 
-    return dt.datetime.fromisoformat(match[1]).replace(tzinfo=dt.timezone.utc)
+    return dt.datetime.strptime(match[1], ISODATE_FORMAT).replace(tzinfo=dt.timezone.utc)
 
 
 def set_status(conn, date, seq=None, indexed=True):

test/python/test_db_status.py

@@ -19,6 +19,11 @@ OSM_NODE_DATA = """\
 </osm>
 """
 
+def iso_date(date):
+    return dt.datetime.strptime(date, nominatim.db.status.ISODATE_FORMAT)\
+               .replace(tzinfo=dt.timezone.utc)
+
+
 def test_compute_database_date_valid(monkeypatch, status_table, place_row, temp_db_conn):
     place_row(osm_type='N', osm_id=45673)
 
@@ -32,7 +37,7 @@ def test_compute_database_date_valid(monkeypatch, status_table, place_row, temp_
     date = nominatim.db.status.compute_database_date(temp_db_conn)
 
     assert requested_url == ['https://www.openstreetmap.org/api/0.6/node/45673/1']
-    assert date == dt.datetime.fromisoformat('2006-01-27T22:09:10').replace(tzinfo=dt.timezone.utc)
+    assert date == iso_date('2006-01-27T22:09:10')
 
 
 def test_compute_database_broken_api(monkeypatch, status_table, place_row, temp_db_conn):

test/python/test_tools_replication.py

@@ -41,7 +41,8 @@ def test_init_replication_success(monkeypatch, status_table, place_row, temp_db_
 
     temp_db_cursor.execute("SELECT * FROM import_status")
 
-    expected_date = dt.datetime.fromisoformat('2006-01-27T19:09:10').replace(tzinfo=dt.timezone.utc)
+    expected_date = dt.datetime.strptime('2006-01-27T19:09:10', status.ISODATE_FORMAT)\
+                        .replace(tzinfo=dt.timezone.utc)
     assert temp_db_cursor.rowcount == 1
     assert temp_db_cursor.fetchone() == [expected_date, 234, True]