User token may not have a tenant

GET /tenants on admin port fails with the following:

[...]
  File "/usr/lib/python2.7/dist-packages/keystone/common/wsgi.py", line 180, in __call__
    result = method(context, **params)
  File "/usr/lib/python2.7/dist-packages/keystone/identity/core.py", line 248, in get_all_tenants
    self.assert_admin(context)
  File "/usr/lib/python2.7/dist-packages/keystone/common/wsgi.py", line 211, in assert_admin
    creds['tenant_id'] = user_token_ref['tenant'].get('id')
AttributeError: 'NoneType' object has no attribute 'get'

This is because the token provided is not related to a tenant.