Writing tests after I took over a project. Getting 'Cannot add foreign key constraint'.

[Adam Heller]

When I took over this project it was in Django 1.5.  I've since incrementally upgraded it and am now running successfully in 1.8.3.  There are also no tests written.  I've decided to write a few tests after adding some new views today.

when i run ./manage.py test apps.public_web, i'm given the option to delete the test_ database, which I accept. Then "django.db.utils.IntegrityError: (1215, 'Cannot add foreign key constraint')" is thrown.  When i execute SHOW ENGINE INNODB STATUS in my database (AWS RDB):

"2015-08-21 19:43:53 2ab145254700 Error in foreign key constraint of table ngv_tests/#sql-996_5247:

 FOREIGN KEY (`content_type_id`) REFERENCES `django_content_type` (`id`):

Cannot resolve table name close to:

 (`id`)"

Any suggestions?