id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
25109	MigrationLoader.load_disk hides ImportError for invalid MIGRATION_MODULES	Daniel Hahler	Berker Peksag	"With an invalid module name in `MIGRATION_MODULES`, you will get a rather confusing `InvalidBasesError`:

{{{
InvalidBasesError: Cannot resolve bases for [<ModelState: 'djangocms_text_ckeditor.Text'>]
This can happen if you are inheriting models from an app with migrations (e.g. contrib.auth)
 in an app with no migrations; see https://docs.djangoproject.com/en/1.8/topics/migrations/#dependencies for more
}}}

This is caused by ignoring the `ImportError` in https://github.com/django/django/blob/d72f8862cb1a39934952e708c3c869be1399846e/django/db/migrations/loader.py#L70-L78, which is meant to handle non-existent migrations.

The following patch might fix it:

{{{
diff --git i/django/db/migrations/loader.py w/django/db/migrations/loader.py
index a8f4be4..e872294 100644
--- i/django/db/migrations/loader.py
+++ w/django/db/migrations/loader.py
@@ -72,7 +72,9 @@ def load_disk(self):
             except ImportError as e:
                 # I hate doing this, but I don't want to squash other import errors.
                 # Might be better to try a directory check directly.
-                if ""No module named"" in str(e) and MIGRATIONS_MODULE_NAME in str(e):
+                if (""No module named"" in str(e)
+                        and MIGRATIONS_MODULE_NAME in str(e)
+                        and app_config.label not in settings.MIGRATION_MODULES):
                     self.unmigrated_apps.add(app_config.label)
                     continue
                 raise
}}}

But then Django's tests itself fail, because they use this ""hack"":

{{{
    settings.MIGRATION_MODULES = {
        # these 'tests.migrations' modules don't actually exist, but this lets
        # us skip creating migrations for the test models.
        'auth': 'django.contrib.auth.tests.migrations',
        'contenttypes': 'contenttypes_tests.migrations',
    }
}}}
([Source](https://github.com/django/django/blob/d72f8862cb1a39934952e708c3c869be1399846e/tests/runtests.py#L142-147))

I've seen this issue multiple times in the context of Django CMS (and its plugins), because in the progress of migrating to Django's migrations they were using modules like `djangocms_text_ckeditor.migrations_django` which then were renamed.

"	Bug	closed	Migrations	dev	Normal	fixed		berker.peksag@…	Ready for checkin	1	0	0	0	0	0