'Callback that fires when the spawner has stopped'

@gen.coroutine
def user_stopped(self, user, server_name):

    spawner = user.spawners[server_name]
    status = (yield spawner.poll())
    if (status is None):
        status = 'unknown'
    self.log.warning('User    %s    server    stopped,    with    exit    code:    %s', user.name, status)
    (yield self.proxy.delete_user(user, server_name))
    (yield user.stop(server_name))
