[Open Stack] error access with horizon

If you have a error similar to :

• First successful login:
  2015-05-11 01:56:11,986 2327 INFO openstack_auth.forms Login successful for user "gtirloni".
• Second unsuccessful login:
  2015-05-11 10:24:30,717 2328 INFO openstack_auth.forms Login successful for user "gtirloni".
  2015-05-11 10:24:30,718 2328 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)
    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/django/contrib/auth/views.py", line 51, in login
      auth_login(request, form.get_user())
    File "/usr/lib/python2.7/site-packages/django/contrib/auth/__init__.py", line 102, in login
      if _get_user_session_key(request) != user.pk or (
    File "/usr/lib/python2.7/site-packages/django/contrib/auth/__init__.py", line 59, in _get_user_session_key
      return get_user_model()._meta.pk.to_python(request.session[SESSION_KEY])
    File "/usr/lib/python2.7/site-packages/django/db/models/fields/__init__.py", line 969, in to_python
      params={'value': value},
  ValidationError: [u"'1550aa46bac146a0ac76e4801a66e065' value must be an integer."]

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