DeprecationWarning: setDaemon() is deprecated, set the daemon attribute instead

[whimboo]

When I run the unit tests I can see the following deprecation warning:

pywebsocket3/msgutil.py:130: DeprecationWarning: setDaemon() is deprecated, set the daemon attribute instead
  self.setDaemon(True)

[ricea]

Okay, so the daemon attribute was added in 2.6 and 3.3.

For Python 2 we only support 2.7 or newer, so that is fine.

The oldest Python 3 version we tested for when Travis was working was 3.5. I don't think we've officially dropped support for older versions, but I think it would be safe to add a requirement for a minimum Python 3 version of 3.3, or maybe even 3.5 since I've no idea whether 3.3 would really work or not.