title: Session value missing after redirect with django python-social-auth
body: <p>I am working on a django project using python-social-auth to do authentication with facebook. I am running the django server on localhost and have facebook set up with my application to redirect to <a href="http://127.0.0.1:8000/complete/facebook/" rel="noreferrer">http://127.0.0.1:8000/complete/facebook/</a>, which begins python-social-auth's pipeline to authenticate a user. I am using postgres as my database. </p>
  
  <p>When this method is called and tries to authenticate, it cannot find information on the session. From <a href="https://github.com/omab/python-social-auth/issues/534" rel="noreferrer">https://github.com/omab/python-social-auth/issues/534</a> , I think the sessionid cookie is being overwritten. If I send the facebook redirect to a different url to load a static page without authentication, there is no error but I am also not authenticating or getting any information from facebook. </p>
  
  <p>How would I go about not overwriting the sessionid cookie -if of course, that is the actual issue- or is there another problem that I might be missing here?</p>
  
  <pre><code>[03/Jun/2016 05:19:58] "GET /login/facebook/?next=/lithium-web/ HTTP/1.1" 302 0
  Internal Server Error: /complete/facebook/
  Traceback (most recent call last):
    File "/Users/mac/Desktop/lithium-web/lib/python2.7/site-packages/django/core/handlers/base.py", line 149, in get_response
      response = self.process_exception_by_middleware(e, request)
    File "/Users/mac/Desktop/lithium-web/lib/python2.7/site-packages/django/core/handlers/base.py", line 147, in get_response
      response = wrapped_callback(request, *callback_args, **callback_kwargs)
    File "/Users/mac/Desktop/lithium-web/lib/python2.7/site-packages/django/views/decorators/cache.py", line 57, in _wrapped_view_func
      response = view_func(request, *args, **kwargs)
    File "/Users/mac/Desktop/lithium-web/lib/python2.7/site-packages/django/views/decorators/csrf.py", line 58, in wrapped_view
      return view_func(*args, **kwargs)
    File "/Users/mac/Desktop/lithium-web/lib/python2.7/site-packages/social/apps/django_app/utils.py", line 51, in wrapper
      return func(request, backend, *args, **kwargs)
    File "/Users/mac/Desktop/lithium-web/lib/python2.7/site-packages/social/apps/django_app/views.py", line 28, in complete
      redirect_name=REDIRECT_FIELD_NAME, *args, **kwargs)
    File "/Users/mac/Desktop/lithium-web/lib/python2.7/site-packages/social/actions.py", line 43, in do_complete
      user = backend.complete(user=user, *args, **kwargs)
    File "/Users/mac/Desktop/lithium-web/lib/python2.7/site-packages/social/backends/base.py", line 41, in complete
      return self.auth_complete(*args, **kwargs)
    File "/Users/mac/Desktop/lithium-web/lib/python2.7/site-packages/social/utils.py", line 229, in wrapper
      return func(*args, **kwargs)
    File "/Users/mac/Desktop/lithium-web/lib/python2.7/site-packages/social/backends/facebook.py", line 71, in auth_complete
      state = self.validate_state()
    File "/Users/mac/Desktop/lithium-web/lib/python2.7/site-packages/social/backends/oauth.py", line 88, in validate_state
      raise AuthStateMissing(self, 'state')
  AuthStateMissing: Session value state missing.
  </code></pre>