Python 2 - support removal

[gonchik]

Hi!

time to skip python 2.x versions. Yes, I waited 5 years until last super old servers will be updated, and last a few months were upgraded.
I am happy to skip python2 support.

Steps:

1. Remove Github actions
2. Remove string formats make for pythonic 3.
3. Update pypi
4. Adjust linter, black
5. Review tests
6. 3.41.x will be latest supported version with python2
7. next release will start from 4.0.0 fully support 3.9 and newer based on the https://devguide.python.org/versions/
8. use more and more python3 sugar codes.

Welcome to contribute.

Cheers,
Gonchik Tsymzhitov