Fixed #6970 -- Raise the original `IntegrityError` when all required fields...

Fixed #6970 -- Raise the original `IntegrityError` when all required fields aren't specified in `get_or_create` instead of a misleading `DoesNotExist` error, thanks deadwisdom.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@8398 bcc190cf-cafb-0310-a4f2-bffc1f526a37