Fixed #14473 -- converted the model_package tests from doctests to unitests. ...

Fixed #14473 -- converted the model_package tests from doctests to unitests.  We have always been at war with doctests.  Thanks to Gabriel Hurley for the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14227 bcc190cf-cafb-0310-a4f2-bffc1f526a37