The method included to patch get_query_set is very broken, and leads to some very bug code in circumstances where managers get subclassed - the behaviour of the subclass can be skipped. This is a very serious error for the case of Related managers, because it means that the limiting of the queryset that is added by the subclass get_query_set method gets skipped, so the related manager queries apply to all objects.

I've created a branch that demonstrates the problem, adding 4 tests, 2 of which fails with Django 1.8, one fails with Django 1.5:

https://github.com/spookylukey/django-compat/tree/get_query_set_patch_bug

I've created a PR so that you can see the tests failing.

The full details are explained in this blog post:

http://lukeplant.me.uk/blog/posts/handling-django's-get_query_set-rename-is-hard/