[Fixed]-Getting a "The following content types are stale and need to be deleted" when trying to do a migrate. What does this mean, and how can I solve it?

The message you get is triggered when you remove/delete a model and do a migration.

In most cases, you can delete them safely. However, in some cases this might result to data loss. If other models have a foreign key to the removed model, these objects will also be deleted.

Here’s the django ticket that requests to make deleting stale content types safer.

EDIT

As @x-yuri pointed, this ticket has been fixed and has been released in Django 1.11.