'Check role of a user on a project.'

def check_user_role_existence_on_project(self, project_id, user_id, role_id):

    (resp, body) = self.head(('projects/%s/users/%s/roles/%s' % (project_id, user_id, role_id)))
    self.expected_success(204, resp.status)
    return rest_client.ResponseBody(resp)
