[bug#46028] [PATCH core-updates v2] gnu: python: Replace PYTHONPATH by GUIX_PYTHONPATH_X_Y.

[Maxim Cournoyer]

Hi,

Maxim Cournoyer <maxim.cournoyer@gmail.com> writes:

> Using PYTHONPATH as a mean to discover the Python packages had the following
> issues:
>
>         1. It is not versioned, so different versions of Python would clash if
>         installed in a shared profile.
>
>         2. It would interfere with the host Python site on foreign
>         distributions, sometimes preventing a a user to login their GDM
>         session (!).
>
>         3. It would take precedence over user installed Python packages
>         installed through pip.
>
>         4. It would leak into Python virtualenvs, which are supposed to create
>         isolated Python environments.

I've adapted the most problematic uses of PYTHONPATH in the code base
(mostly (getenv "PYTHONPATH"), which would typically now return #f and
pushed the branch to cu/farewell-to-pythonpath (it contains ~160
commits, so I thought it'd be easier to review as a branch).

Thanks!

Maxim