Upgraded Python version support to recent versions

[claudep]

Dropped Python 3.7, 3.8, 3.9 (EOL).
Added Python 3.11, 3.12, 3.13

[claudep]

@asedeno, do you think you would be able to help us make the xapian build step pass again?

[asedeno]

It works fine with Xapian 1.4.20, and Xapian 1.4.31 (latest).

[claudep]

Ah yes, the prebuilding step now passes, thanks a lot! I will try to work on on other issues.

[claudep]

@asedeno, the coveralls step fails, and I don't see how to fix it. Do we really need that coveralls stuff?

[asedeno]

This seems to be related to the PYTHONPATH stuff, which was copied over from the old travis CI config.
We do need . in PYTHONPATH for a bunch of stuff to work. I'm looking into how to better do this now.

[asedeno]

Let's give this a shot. Adding /usr/lib/python3/dist-packages to PYTHONPATH is weird, and when I did that I could replicate the issue we're seeing in tests. I think the only thing we were getting out of there is packaging, which is a django-haystack dependency we are not installing. Let's install it and get rid of this hack.

[coveralls]

coverage: 97.588% (+0.02%) from 97.565%
when pulling c53e06b on claudep:upgradepython
into 30c727e on notanumber:master.

[claudep]

@asedeno You are my hero 🏅 Thanks a lot.