Parallel test runner runs system checks with database aliases before those aliases are set up

[Jacob Walls]

#36083 made the parallel test runner run system checks in workers. Well and good, but the call is done before database aliases are set up.

This should explain the recent failures with the geodjango label on Github Actions, also reproducible locally, with errors like:

django.db.utils.OperationalError: connection failed: connection to server on socket "/var/run/postgresql/.s.PGSQL.5432" failed: FATAL:  database "django-postgis-other" does not exist

I'm showing this is fixed with:

django/test/runner.py

@@ -463 +463 @@
             process_setup(*process_setup_args)
         django.setup()
         setup_test_environment(debug=debug_mode)
-        call_command(
-            "check", stdout=io.StringIO(), stderr=io.StringIO(), databases=used_aliases
-        )
 
     db_aliases = used_aliases if used_aliases is not None else connections
     for alias in db_aliases:
@@ -477 +474 @@
                 connection._test_serialized_contents = value
         connection.creation.setup_worker_connection(_worker_id)
 
+    if is_spawn_or_forkserver:
+        call_command(
+            "check", stdout=io.StringIO(), stderr=io.StringIO(), databases=used_aliases
+        )
 
 def _run_subsuite(args):
     """

Regression in 606fc352799e372928fa2c978ab99f0fb6d6017c.

Interestingly, this specific failure did not manifest until e8190b370e508648b0f0ee9b86876f97d3997e14.

[Natalia Bidart]

Thank you Jacob for investigating and fixing this!

[Jacob Walls]

​PR