Python conflicts.

[Ricardo Wurmus]

Hi Guix,

there are two things related to the installation of Python modules that
I would like to see changed; but as I may not understand what side
effects the proposed changes might have I'd like to gather some opinions
first.

1) Nosetests

Installing Python modules that have an input "python-nose" (always?)
install "$out/bin/nosetests" and various wrappers around this script.
This script is not very useful for a user of the module as it only runs
the test suite.  As we're often propagating Python module inputs, the
installation of one Python module usually results in conflicts with the
various versions of "$out/bin/nosetests" that are to be installed into
the profile.

This makes the nosetests scripts even less useful as an arbitrary
version will end up in the profile.  I'd like to exclude them from
installation in all Python packages, maybe by modifying
"python-build-system" such that the files are deleted from the output
directory again.

What I don't like about using the "python-build-system" for this is that
"$out/bin/nosetests" is only created when "python-nose" (or
"python2-nose") is a package input.  Is there a better way?  Can we
prevent the creation of the "nosetests" script (and its wrappers), maybe
with some flag to setuptools?

2) lib/python$version/site-packages/site.{py,pyc}

Another file that frequently causes conflicts is "site.py" (and its
compiled cousin).  It seems to me that "site.py" doesn't contain any
module-specific information and is probably the same for all modules.  I
would like to change "python-build-system" such that Python modules do
not install this file at all.

The only problem I see is that the "python" package itself does not come
with this file.  If it should be provided at all I think that it should
come from the "python" package, rather than any of the modules that may
or may not be installed.

What do you think?

~~ Ricardo