[Answer]-Django: Internal Server Error

According to the documentation:

New in Django 1.7.

Allows a user’s sessions to be invalidated when their password changes. See Session invalidation on password change for details. This middleware must appear after django.contrib.auth.middleware.AuthenticationMiddleware in MIDDLEWARE_CLASSES.

Thus, my guess is that you are not on Django 1.7+, yet you have defined the django.contrib.auth.middleware.SessionAuthenticationMiddleware in the MIDDLEWARE_CLASSES.

<= Django 1.6

See the Sessions Documentation.

To enable session functionality, do the following:

Edit the MIDDLEWARE_CLASSES setting and make sure it contains 'django.contrib.sessions.middleware.SessionMiddleware'. The default settings.py created by django-admin.py startproject has SessionMiddleware activated.

If you don’t want to use sessions, you might as well remove the SessionMiddleware line from MIDDLEWARE_CLASSES and 'django.contrib.sessions' from your INSTALLED_APPS. It’ll save you a small bit of overhead.