Drop support for Python 2

[Viicos]

Originally posted by @chriselion in #1262 (comment)

Python 3.2 seems to be the minimum required version, as functools.total_ordering is used in some places.

If this is ok, I can go through the codebase and remove obsolete code related to Python2 compatibility. This would make it possible for me to catch anything that would require a higher version of Python

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[Viicos]

We could even raise the required version to 3.8? And remove six integration

[Viicos]

Handled since then.