Sentry 问题

在服务器上装好了sentry客户端用一个测试代码，根据这个来的
http://raven.readthedocs.org/en/latest/integrations/logging.html

logger.error('There was some %s error', 'crazy')

这样没有问题，服务器端登陆网页能看到信息被记录下来，但如果这样

logger.error('There was some crazy error', exc_info=True)
就会出现这样的错误：

```
Top level Sentry exception caught - failed creating log record
b'There was some crazy error'
b'Traceback (most recent call last):\n File "C:\\Python33\\lib\\site-packages\\raven\\handlers\\logging.py", line 59, in emit\n self.format(record)\n File "C:\\Python33\\lib\\logging\\__init__.py", line 808, in format\n return fmt.format(record)\n File "C:\\Python33\\lib\\logging\\__init__.py", line 554, in format\n record.exc_text = self.formatException(record.exc_info)\n File "C:\\Python33\\lib\\logging\\__init__.py", line 504, in formatException\n traceback.print_exception(ei[0], ei[1], tb, None, sio)\n File "C:\\Python33\\lib\\traceback.py", line 156, in print_exception\n for value, tb in values:\n File "C:\\Python33\\lib\\traceback.py", line 122, in _iter_chain\n context = exc.__context__\nAttributeError: \'NoneType\' object has no attribute \'__context__\'\n'
Sentry is attempting to send 1 pending error messages
Waiting up to 10 seconds
Press Ctrl-Break to quit
```

请问是怎么回事