Fixed #7922 -- admin.autodiscover() no longer eats ImportErrors for breakfast....

Fixed #7922 -- admin.autodiscover() no longer eats ImportErrors for breakfast. Thanks Jan Rademaker and Alex Gaynor for their work on the ticket.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@8174 bcc190cf-cafb-0310-a4f2-bffc1f526a37