'list roles of a group on a domain.'

def list_group_roles_on_domain(self, domain_id, group_id):

    (resp, body) = self.get(('domains/%s/groups/%s/roles' % (domain_id, group_id)))
    self.expected_success(200, resp.status)
    body = json.loads(body)
    return rest_client.ResponseBody(resp, body)
