Comment 1 for bug 1204214

assignment/core.py:
    def _get_group_project_roles():
        ...
       metadata_ref = self._get_metadata(
                           group_id=x['id'],
                            domain_id=project_ref['domain_id'])

self._get_metadata() gets called with user_id=None

assignment/backends/ldap.py:
    def _get_metadata():
        ...
        if (not self.get_project(tenant_id) or
                user_id and not self.identity_api.get_user(user_id)):

self.identity_api.get_user(user_id) raises "user not found" since user_id = None