Cannot modify Active Directory project members in Horizon as admin

Issue

• Receive error in Horizon when attempting to modify project/tenant users: "Danger: There was an error submitting the form. Please try again"
• Also observe the following error in the horizon log:

2016-05-03 16:12:38,543 45957 ERROR django.request Internal Server Error: /dashboard/identity/<uuid>/update/
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/django/core/handlers/base.py", line 112, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/lib/python2.7/site-packages/horizon/decorators.py", line 36, in dec
    return view_func(request, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/horizon/decorators.py", line 52, in dec
    return view_func(request, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/horizon/decorators.py", line 36, in dec
    return view_func(request, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/django/views/generic/base.py", line 69, in view
    return self.dispatch(request, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/django/views/generic/base.py", line 87, in dispatch
    return handler(request, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/horizon/workflows/views.py", line 165, in post
    context = self.get_context_data(**kwargs)
  File "/usr/lib/python2.7/site-packages/horizon/workflows/views.py", line 89, in get_context_data
    workflow = self.get_workflow()
  File "/usr/lib/python2.7/site-packages/horizon/workflows/views.py", line 79, in get_workflow
    entry_point=entry_point)
  File "/usr/share/openstack-dashboard/openstack_dashboard/wsgi/../../openstack_dashboard/dashboards/identity/projects/workflows.py", line 546, in __init__
    **kwargs)
  File "/usr/lib/python2.7/site-packages/horizon/workflows/base.py", line 648, in __init__
    valid = step.action.is_valid()
  File "/usr/lib/python2.7/site-packages/django/forms/forms.py", line 129, in is_valid
    return self.is_bound and not bool(self.errors)
  File "/usr/lib/python2.7/site-packages/django/forms/forms.py", line 121, in errors
    self.full_clean()
  File "/usr/lib/python2.7/site-packages/django/forms/forms.py", line 274, in full_clean
    self._clean_form()
  File "/usr/lib/python2.7/site-packages/django/forms/forms.py", line 300, in _clean_form
    self.cleaned_data = self.clean()
  File "/usr/share/openstack-dashboard/openstack_dashboard/wsgi/../../openstack_dashboard/dashboards/identity/projects/workflows.py", line 91, in clean
    self.request, tenant_id=self.initial['project_id'])
  File "/usr/lib/python2.7/site-packages/horizon/utils/memoized.py", line 90, in wrapped
    value = cache[key] = func(*args, **kwargs)
  File "/usr/share/openstack-dashboard/openstack_dashboard/wsgi/../../openstack_dashboard/usage/quotas.py", line 262, in tenant_quota_usages
    snapshots = cinder.volume_snapshot_list(request, opts)
  File "/usr/share/openstack-dashboard/openstack_dashboard/wsgi/../../openstack_dashboard/api/cinder.py", line 282, in volume_snapshot_list
    search_opts=search_opts)]
  File "/usr/lib/python2.7/site-packages/cinderclient/v1/volume_snapshots.py", line 136, in list
    "snapshots")
  File "/usr/lib/python2.7/site-packages/cinderclient/base.py", line 70, in _list
    resp, body = self.api.client.get(url)
  File "/usr/lib/python2.7/site-packages/cinderclient/client.py", line 302, in get
    return self._cs_request(url, 'GET', **kwargs)
  File "/usr/lib/python2.7/site-packages/cinderclient/client.py", line 269, in _cs_request
    **kwargs)
  File "/usr/lib/python2.7/site-packages/cinderclient/client.py", line 252, in request
    raise exceptions.from_response(resp, body)
ClientException: The server has either erred or is incapable of performing the requested operation. (HTTP 500) (Request-ID: req-<id>)

• Error seen in cinder api log:

2016-05-03 09:55:50.275 13712 TRACE cinder.api.middleware.fault InvalidRequestError: Entity '<class 'cinder.db.sqlalchemy.models.Snapshot'>' has no property 'tenant_id'