Description of problem:
unable to login to horizon after session timeout. following error in the horizon.log

2015-09-13 01:36:55,232 24474 ERROR django.request Internal Server Error: /dashboard/auth/login/
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/django/core/handlers/base.py", line 132, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/lib/python2.7/site-packages/django/views/decorators/debug.py", line 76, in sensitive_post_parameters_wrapper
    return view(request, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/django/utils/decorators.py", line 110, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/django/views/decorators/cache.py", line 57, in _wrapped_view_func
    response = view_func(request, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/openstack_auth/views.py", line 111, in login
    **kwargs)

Version-Release number of selected component (if applicable):

python-django-horizon-2015.1.1-1.el7.noarch
python-django-openstack-auth-1.2.0-4.el7.noarch

How reproducible:
Every time

Steps to Reproduce:
1. Login
2. Allow session to timeout
3. Login again

Actual results:
Horizon returns an error.

Expected results:
Horizon should not return an error

Additional info:
clearing the cache/cookies on the browser allows me to log back in.