Py3: Use feature detection, not version detection
Py3: Use feature detection, not version detection

__Problem:__ The current compatibility code breaks Python 3 porting guidelines by using version detection instead of feature detection.  It would for instance, would fail under Python 4 and above.

__Solution:__ Follow the Python 3 porting guide best practice: __Use feature detection instead of version detection__.

https://docs.python.org/3/howto/pyporting.html#use-feature-detection-instead-of-version-detection
zeromq/zproject,zeromq/zproject,paddor/zproject,zeromq/zproject,paddor/zproject,paddor/zproject