tests: fix sql_alchemy_db fixture for timescale

there's a deadlock error that happens where the timescale background
worker is running background jobs and we're altering the schema of
the tables on which it's running the background job on, so we stop the
background worker momentarily to allow the migrations to run.

Author: joseph-sentry

conftest.py

@@ -122,11 +122,23 @@ def sqlalchemy_db(request: pytest.FixtureRequest, django_db_blocker, django_db_s
         original_test_name = settings.DATABASES["default"]["TEST"]["NAME"]
         settings.DATABASES["default"]["NAME"] = "sqlalchemy"
         settings.DATABASES["default"]["TEST"]["NAME"] = "test_postgres_sqlalchemy"
+        for connection in connections:
+            if "timeseries" in connection:
+                with connections[connection].cursor() as cursor:
+                    cursor.execute(
+                        "SELECT _timescaledb_internal.stop_background_workers();"
+                    )
         db_cfg = setup_databases(
             verbosity=request.config.option.verbose,
             interactive=False,
             keepdb=keepdb,
         )
+        for connection in connections:
+            if "timeseries" in connection:
+                with connections[connection].cursor() as cursor:
+                    cursor.execute(
+                        "SELECT _timescaledb_internal.start_background_workers();"
+                    )
         settings.DATABASES["default"]["NAME"] = original_db_name
         settings.DATABASES["default"]["TEST"]["NAME"] = original_test_name