Missing django.contrib.auth.context_processors.auth dependency for django.contrib.admin app

[kowal-tbg]

As we can see here:
​https://github.com/django/django/blob/stable/1.8.x/django/contrib/admin/sites.py#L191-196
the django.contrib.admin application requires django.contrib.auth.context_processors.auth, but the current documentation:
​https://docs.djangoproject.com/en/1.8/ref/contrib/admin/
does not mention it. I received the ImproperlyConfigured exception when I tried to do 'makemigrations' after enabling django.contrib.admin according to the documentation in my project. This also may affect other Django versions.

[Tim Graham <timograham@…>]

In f59667c:

Fixed #25033 -- Added context_processors.auth to documented admin dependencies.

[Tim Graham <timograham@…>]

In 8922266a:

[1.8.x] Fixed #25033 -- Added context_processors.auth to documented admin dependencies.

Backport of f59667c121272ba7a1161e8bc4787654d929f6f1 from master