django-recurrence/django-recurrence — pull request #22 by mbertheau (2014-09-26 08:57:05+00:00)
Title: Don't break Django-1.7 migrations

This reverts part of a201e23. An IntegrityError is exactly the right exception
that should be raised when trying to save None into a field with null=False.

Django-1.7 migrations ask for the db_prep_value for None and don't handle that
exception there.