Remove or replace python 2 from CI

[sevdog]

Github actions has dropped support to python 2 in actions sinc 19th June 2023:
actions/setup-python#672

It is required to choose if the best choise is to trop support for python 2 (and thus for django <2), which is EOL since 1st Januery 2020, or to use something different to test against it.