Django is swallowing ImportErrors in migrations for modules containing the string 'south'

[Gavin Wahl]

If I put from mymodule import north, east, west, south, xxxdoesntexistxxx in an initial migration, Django tells me:

django.db.migrations.exceptions.BadMigrationError: Migrated app 'foo' contains South migrations. Make sure all numbered South migrations are deleted prior to creating Django migrations.

I should get an ImportError so I can debug the problem.

[Tim Graham]

That error message was added in #25618 but I guess reverting it won't fix the issue either. I think this issue affects 1.8 and 1.7 too (silently putting apps with such errors in unmigrated_apps before #25618), but perhaps we could backport c4af8eb366be45420e13a400cc1dcc8fab91c1ad to 1.9. I expect South is probably obsoleted by Django 1.9 too but I didn't want to backport a non-release blocker at this point without a better justification.

[Tim Graham <timograham@…>]

In 9e7d0d9:

[1.9.x] Fixed #25627, refs #25618 -- Removed detection of south migrations in loader.

Backport of c4af8eb366be45420e13a400cc1dcc8fab91c1ad from master