Roll back forceful assignment of PATH when invoking a local process

[motus]

Roll back one of the updates from #705
It breaks tests on both Windows and WSL DevContainer on my PC.

• On Windows, environ may not have PATH at all
• On my WSL DevContainer, passing non-null env to subprocess.run prevents it from finding the right python interpreter

[bpkroth]

Approving to unblock, but I think we'll need to revisit (see comments in the PR).

[bpkroth]

On Windows, environ may not have PATH at all

That seems like a bug. PATH is used to resolve command locations on both platforms.

On my WSL DevContainer, passing non-null env to subprocess.run prevents it from finding the right python interpreter

Oh that's interesting. That's exactly the situation I was trying to fix, but in the opposite direction. Do you have an example?