How to force a user logout in Django?

Question

In my Django app under certain conditions I want to be able to force users to log out by a username. Not necessarily the current user who is logged in, but another user. So,

Answer 1

As Tony Abou-Assaleh, I also needed to log out users who were set to inactive, so I started by implementing his solution. After some time I found out that the middleware is forcing a DB query on all requests (to check if the user was blocked), and thus hurts performance on pages that doesn't require login.

I have a custom user object and Django >= 1.7, so what I ended up doing is overriding its get_session_auth_hash function to invalidate the session when the user is inactive. A possible implementation is:

def get_session_auth_hash(self):
    if not self.is_active:
        return "inactive"
    return super(MyCustomUser, self).get_session_auth_hash()

For this to work, django.contrib.auth.middleware.SessionAuthenticationMiddleware should be in settings.MIDDLEWARE_CLASSES