restrict use of os.environ in Configuration

Only use the OS environment, when the environ parameter is set
to None. Currently it would use the OS env on an empty dict.

src/nominatim_db/config.py

@@ -61,7 +61,7 @@ class Configuration:
 
     def __init__(self, project_dir: Optional[Union[Path, str]],
                  environ: Optional[Mapping[str, str]] = None) -> None:
-        self.environ = environ or os.environ
+        self.environ = os.environ if environ is None else environ
         self.config_dir = paths.CONFIG_DIR
         self._config = dotenv_values(str(self.config_dir / 'env.defaults'))
         if project_dir is not None:

test/python/api/search/test_icu_query_analyzer.py

@@ -38,7 +38,7 @@ async def conn(table_factory):
     table_factory('word',
                   definition='word_id INT, word_token TEXT, type TEXT, word TEXT, info JSONB')
 
-    async with NominatimAPIAsync(environ={}) as api:
+    async with NominatimAPIAsync() as api:
         async with api.begin() as conn:
             yield conn
 

test/python/api/search/test_legacy_query_analyzer.py

@@ -72,7 +72,7 @@ async def conn(table_factory, temp_db_cursor):
     temp_db_cursor.execute("""CREATE OR REPLACE FUNCTION make_standard_name(name TEXT)
                               RETURNS TEXT AS $$ SELECT lower(name); $$ LANGUAGE SQL;""")
 
-    async with NominatimAPIAsync(environ={}) as api:
+    async with NominatimAPIAsync() as api:
         async with api.begin() as conn:
             yield conn
 

test/python/api/test_api_status.py

@@ -45,7 +45,7 @@ def test_status_full(apiobj, frontend):
 def test_status_database_not_found(monkeypatch):
     monkeypatch.setenv('NOMINATIM_DATABASE_DSN', 'dbname=rgjdfkgjedkrgdfkngdfkg')
 
-    api = napi.NominatimAPI(environ={})
+    api = napi.NominatimAPI()
 
     result = api.status()