REV: 1.13.x: revert changes to f2py and tempita handling in meson.build files

[rgommers]

Reverts the last two commits of gh-20121. Those were not robust against Meson picking up a different Python interpreter for which numpy and/or cython were not installed. This is rare, but can happen when a distro builds for a non-default version of Python and disables build isolation.

Addresses the issue reported in gh-20535 in the 1.13.x branch. Leaving the issue open because I'd like a different change in main. In a release branch a straight revert seems best though, since we had no issues opened related to this for 1.12.x.

[tylerjereddy]

I spent some time trying to reproduce and actually failed even with various attempts at aliasing python3 to something else and disabling build isolation. I think things are fairly robust already with i.e., venv on Ubuntu even if I make sure that python3 points to something without TPL installs.

Anyway, probably not worth me trying to repro in docker or something. I'll go ahead and merge.

There are some CI failures that are not related, some are connectivity we can ignore, but others may need investigating on the release branch so I'll open an issue for those.

[tylerjereddy]

thanks

[rgommers]

I think I could write a CI job that covers this, and I may do so at some point - but it'd be time-consuming to fiddle with for sure.

[bnavigator]

I spent some time trying to reproduce and actually failed even with various attempts at aliasing python3 to something else and disabling build isolation. I think things are fairly robust already with i.e., venv on Ubuntu even if I make sure that python3 points to something without TPL installs.

I gave you a reproducer in gh-20535, didn't I? Make sure the shebang hardcoded interpreter /usr/bin/python3 does not have numpy and f2py installed (/usr/lib.../site-packages) and a non-isolated build will fail.

[tylerjereddy]

I gave you a reproducer in #20535, didn't I?

Not really, I spent quite some time trying to reproduce in a venv on Ubuntu Linux, and meson was smart enough to do the right thing time and time again. Same thing on MacOS too, to be honest. I understood your basic complaint, but I don't buy that the reproducer is fully trivial and portable to venvs with a naive python3 more broadly just yet.