Django: NoneType has no attribute _base_manager with Generic relations

If you are using Django's generic framework and receive an AttributeError: 'NoneType' object has no attribute '_base_manager' it's likely that the cause is that the related model's app is missing from your INSTALLED_APPS setting.

If you don't want the app installed you can chuck an import in the module you're attempting to access the relation: from appname.models import RelatedModel