Migrate from Python 2 to Python 3

[pabs3]

Forwarding https://bugs.debian.org/937434

Python 2 is EOL soon so distros are working on removing all modules that require Python 2. Consequently pyew got removed from Debian and will become unusable on most distributions released in the next few years as they remove Python 2 modules and runtimes. Migrating the codebase to Python 3 so that pyew can be used after 2020 would be a good idea.

https://pythonclock.org/
https://bugs.debian.org/939059

PS:

[joxeankoret]

I don't think it's worth the effort required to port Pyew to Python 3, honestly. I don't have the time, neither the need, to support it. However, I would accept patches for it.