ci: python -> python3

[Alizter]

The ubuntu package python was obsolete and has now been removed. We switch to the recommended python3 instead.

[Alizter]

@jdchristensen I will wait until CI is green and then go ahead and merge.

[Alizter]

alectryon has failed, I will investigate.

[Alizter]

I've pushed a commit that hopefully fixes the issue (honestly I have no idea). We will have to wait and see.

[Alizter]

cc @JasonGross in case you have a better idea of what to do.

FTR the error in the CI was:

python3-dev (3.11.2-1+b1) ...
Processing triggers for libc-bin (2.36-9+deb12u7) ...
+ (script @ line 7) $ python3 -m pip install --user --upgrade pygments dominate beautifulsoup4 docutils==0.17.1
error: externally-managed-environment

× This environment is externally managed
╰─> To install Python packages system-wide, try apt install
    python3-xyz, where xyz is the package you are trying to
    install.
    
    If you wish to install a non-Debian-packaged Python package,
    create a virtual environment using python3 -m venv path/to/venv.
    Then use path/to/venv/bin/python and path/to/venv/bin/pip. Make
    sure you have python3-full installed.
    
    If you wish to install a non-Debian packaged Python application,
    it may be easiest to use pipx install xyz, which will manage a
    virtual environment for you. Make sure you have pipx installed.
    
    See /usr/share/doc/python3.11/README.venv for more information.

note: If you believe this is a mistake, please contact your Python installation or OS distribution provider. You can override this, at the risk of breaking your Python installation or OS, by passing --break-system-packages.
hint: See PEP 668 for the detailed specification.

[Alizter]

Hmm didn't seem to work. I will have to take another look later.

[jdchristensen]

I'm pushing a commit that tries to fix this by fixing the permissions earlier.