error when login dashboard

[Sun Jing]

when login dashboard without any operation for 40 minutes,then you need login again,and there will be an error :"An unexpected error has occurred. Try refreshing the page. If that doesn't "
"help, contact your local administrator."

In file /var/log/horizon/horizon.log , it shows:
2015-07-30 08:10:56,451 26786 INFO openstack_auth.forms Login successful for user "admin".
2015-07-30 08:10:56,451 26786 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'\u201926dee20cfa504431af61b0e2a7986cdf\u2018 \u5fc5\u987b\u4e3a\u6574\u6570\u3002']

[Austin Grice (amgrice)]

I'm getting an issue as well with memcache as the caching mechanism

[Thu Sep 10 20:23:15.615461 2015] [:error] [pid 2651] Internal Server Error: /dashboard/auth/login/
[Thu Sep 10 20:23:15.615474 2015] [:error] [pid 2651] Traceback (most recent call last):
[Thu Sep 10 20:23:15.615477 2015] [:error] [pid 2651] File "/usr/lib/python2.7/site-packages/django/core/handlers/base.py", line 132, in get_response
[Thu Sep 10 20:23:15.615479 2015] [:error] [pid 2651] response = wrapped_callback(request, *callback_args, **callback_kwargs)
[Thu Sep 10 20:23:15.615482 2015] [:error] [pid 2651] File "/usr/lib/python2.7/site-packages/django/views/decorators/debug.py", line 76, in sensitive_post_parameters_wrapper
[Thu Sep 10 20:23:15.615484 2015] [:error] [pid 2651] return view(request, *args, **kwargs)
[Thu Sep 10 20:23:15.615487 2015] [:error] [pid 2651] File "/usr/lib/python2.7/site-packages/django/utils/decorators.py", line 110, in _wrapped_view
[Thu Sep 10 20:23:15.615489 2015] [:error] [pid 2651] response = view_func(request, *args, **kwargs)
[Thu Sep 10 20:23:15.615491 2015] [:error] [pid 2651] File "/usr/lib/python2.7/site-packages/django/views/decorators/cache.py", line 57, in _wrapped_view_func
[Thu Sep 10 20:23:15.615493 2015] [:error] [pid 2651] response = view_func(request, *args, **kwargs)
[Thu Sep 10 20:23:15.615495 2015] [:error] [pid 2651] File "/usr/lib/python2.7/site-packages/openstack_auth/views.py", line 111, in login
[Thu Sep 10 20:23:15.615497 2015] [:error] [pid 2651] **kwargs)
[Thu Sep 10 20:23:15.615516 2015] [:error] [pid 2651] File "/usr/lib/python2.7/site-packages/django/views/decorators/debug.py", line 76, in sensitive_post_parameters_wrapper
[Thu Sep 10 20:23:15.615519 2015] [:error] [pid 2651] return view(request, *args, **kwargs)
[Thu Sep 10 20:23:15.615521 2015] [:error] [pid 2651] File "/usr/lib/python2.7/site-packages/django/utils/decorators.py", line 110, in _wrapped_view
[Thu Sep 10 20:23:15.615523 2015] [:error] [pid 2651] response = view_func(request, *args, **kwargs)
[Thu Sep 10 20:23:15.615525 2015] [:error] [pid 2651] File "/usr/lib/python2.7/site-packages/django/views/decorators/cache.py", line 57, in _wrapped_view_func
[Thu Sep 10 20:23:15.615527 2015] [:error] [pid 2651] response = view_func(request, *args, **kwargs)
[Thu Sep 10 20:23:15.615529 2015] [:error] [pid 2651] File "/usr/lib/python2.7/site-packages/django/contrib/auth/views.py", line 51, in login
[Thu Sep 10 20:23:15.615531 2015] [:error] [pid 2651] auth_login(request, form.get_user())
[Thu Sep 10 20:23:15.615533 2015] [:error] [pid 2651] File "/usr/lib/python2.7/site-packages/django/contrib/auth/__init__.py", line 102, in login
[Thu Sep 10 20:23:15.615535 2015] [:error] [pid 2651] if _get_user_session_key(request) != user.pk or (
[Thu Sep 10 20:23:15.615537 2015] [:error] [pid 2651] File "/usr/lib/python2.7/site-packages/django/contrib/auth/__init__.py", line 59, in _get_user_session_key
[Thu Sep 10 20:23:15.615539 2015] [:error] [pid 2651] return get_user_model()._meta.pk.to_python(request.session[SESSION_KEY])
[Thu Sep 10 20:23:15.615541 2015] [:error] [pid 2651] File "/usr/lib/pyth...