contrib.auth @ 1.8b1 breaks existing projects / applications using Mongoengine

[Carsten Klein]

The following changes in django/contrib/auth/init.py

root@J101829:/tmp# diff dj18a1/contrib/auth/__init__.py dj18b1/contrib/auth/__init__.py
55a56,62
> def _get_user_session_key(request):
>     # This value in the session is always serialized to a string, so we need
>     # to convert it back to Python whenever we access it.
>     raise Exception(get_user_model())
>     return get_user_model()._meta.pk.to_python(request.session[SESSION_KEY])
> 
> 
96c103
<         if request.session[SESSION_KEY] != user.pk or (
---
>         if _get_user_session_key(request) != user.pk or (
105c112
<     request.session[SESSION_KEY] = user.pk
---
>     request.session[SESSION_KEY] = user._meta.pk.value_to_string(user)
161c168
<         user_id = request.session[SESSION_KEY]
---
>         user_id = _get_user_session_key(request)

2. Break existing applications / projects using Mongoengine.

Mongoengine installs a custom MongoUser that is a shim around the actual model, which is a mongoengine document. The actual user id is a hexadecimal number / string and might not be validated using int(), causing the following exception

ValidationError at /backend/admin/
[u'\u201a511a1da669fe60752b000000\u201b Wert muss eine Ganzzahl sein.']
Request Method:	GET
Request URL:	http://XXX/login
Django Version:	1.8b1
Exception Type:	ValidationError
Exception Value:	
[u'\u201a511a1da669fe60752b000000\u201b Value must be an int.']
Exception Location:	/usr/local/lib/python2.7/dist-packages/django/db/models/fields/__init__.py in to_python, line 969
Python Executable:	/usr/bin/uwsgi-core
Python Version:	2.7.8