Passing timeout=0 to poll() behaves like poll_forever

[ami-friedman]

Steps to reproduce:

Call poll() with timeout = 0

Expected:
poll() should exit immediately after one attempt (at least this is how poll() behaves in linux)

Actual:
poll() continues until condition is met (basically as if poll_forever was set to True)

This seems to be the problematic line:
max_time = time.time() + timeout if timeout else None

In Python 0 evaluates as False. i think a more correct code would be:
max_time = time.time() + timeout if timeout is not None else None

If this IS intentional, I think it's worth updating the docs