Eventlet抛出不可理解的异常

Question

我正在使用此处的Eventlet示例代码：http://eventlet.net/doc/examples.html#producer-consumer-recursive-web-crawler

在运行途中，我遇到以下多个实例：

Traceback (most recent call last):
  File "/usr/local/lib/python2.6/dist-packages/eventlet-0.9.9-py2.6.egg/eventlet/hubs/hub.py", line 285, in fire_timers
    timer()
  File "/usr/local/lib/python2.6/dist-packages/eventlet-0.9.9-py2.6.egg/eventlet/hubs/timer.py", line 56, in __call__
    cb(*args, **kw)
TypeError: exceptions must be classes, or instances, not bool