select.poll returning strange file descriptors.

[Simon Wittber]

Solved.

I was using poll.register(fileno) without any flags specfied, which
means "tell me when _anything_ happens".

Because of this, I was receiving OOB data, which seems to use strange
fileno values.

to fix this, I now use this:

poll.register(sock.fileno(), select.POLLIN|select.POLLOUT|
select.POLLERR|select.POLLHUP)