[discussion] drop or simplify pip & venv magic during configure

As we have seen in !1235 (merged), the automagic handling of python dependencies leads to a couple of strange problems, e.g. packages installed automatically by cmake are not always found.

I would like to start a discussion on how we can simply this whole cmake-venv-pip integration. My provocative statement is that it leads to more problems than it solves and that a clear error message about missing dependencies would be far more helpful.

Opinions?