Python2.7 in CI not supported anymore

[Robin-Van-de-Merghel]

Issue

We use a docker image with 2.7 in it, it uses an old debian docker with python2.7 embed in it.

Because the debian image (not python2, the debian version itself) is deprecated, while apt update-ing, it will lead to a 404 because mirrors don't support it anymore.

Solution

Two cases:

1. Still support python2.7, use mamba/conda
2. Don't officially support python2.7

[fstagni]

For what concerns the CI, it's "just not supported", and we accept that (in a sense, we can even close already this ticket)

One day we'll remove all the py2 stuff from the code and finally forget about it, but as said other times it's mostly a collective political decision to make (not related to this issue).