App with default_app_config in init crashes

[Iuri de Silvio]

If I don't have an apps.py and the default_app_config is in __init__.py, it fails.

Traceback (most recent call last):
  File "./manage.py", line 22, in <module>
    main()
  File "./manage.py", line 18, in main
    execute_from_command_line(sys.argv)
  File "django/core/management/__init__.py", line 401, in execute_from_command_line
    utility.execute()
  File "django/core/management/__init__.py", line 377, in execute
    django.setup()
  File "django/__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "django/apps/registry.py", line 91, in populate
    app_config = AppConfig.create(entry)
  File "django/apps/config.py", line 157, in create
    if new_entry == app_config_name:
UnboundLocalError: local variable 'app_config_name' referenced before assignment

If the apps.py is there, but the default_app_config is in __init__.py, it fails too.

Traceback (most recent call last):
  File "django/django/test/utils.py", line 381, in inner
    return func(*args, **kwargs)
  File "django/tests/apps/tests.py", line 541, in test_explicit_default_app_config_with_empty_apps
    with self.settings(INSTALLED_APPS=['apps.explicit_default_config_with_empty_apps']):
  File "django/django/test/utils.py", line 336, in __enter__
    return self.enable()
  File "django/django/test/utils.py", line 410, in enable
    apps.set_installed_apps(self.options['INSTALLED_APPS'])
  File "django/django/apps/registry.py", line 355, in set_installed_apps
    self.populate(installed)
  File "django/django/apps/registry.py", line 91, in populate
    app_config = AppConfig.create(entry)
  File "django/django/apps/config.py", line 160, in create
    if new_entry == app_config_name:
UnboundLocalError: local variable 'app_config_name' referenced before assignment

Looks like a regression added in https://code.djangoproject.com/ticket/31180.