Remove support for venv package

venv struggles with the system interpreter found by CMake being in a virtualenv. virtualenv does not suffer the same problem. As this is a quite common user setup, the commit removes support for the venv package.

This only affects the optional virtualenv feature that needs explicit activation.

As I said yesterday, I'm really not in favor of forcing people to use virtualenv on Python 3 - venv is part of the Python distribution for a reason. And to be honest, while some users will have their system Python in a virtualenv, I'd say there's a lot more users who don't...

As far as I understood, venv doesn't support nesting virtualenvs, so we might detect that case using the method shown in https://stackoverflow.com/questions/1871549/determine-if-python-is-running-inside-virtualenv or something similar and require virtualenv in that case.

mentioned in merge request !560 (merged)

That is exactly what we are doing already. I am closing this in favor of !560 (merged) .

closed

mentioned in commit cde3ff09