Missing reference to issue in subprocess documentation

[swaldhoer]

Documentation

https://docs.python.org/3/library/subprocess.html#disabling-use-of-vfork-or-posix-spawn references

subprocess._USE_VFORK = False  # See CPython issue gh-NNNNNN.

subprocess._USE_POSIX_SPAWN = False  # See CPython issue gh-NNNNNN.

These are the only missing references I found in the whole docs.

I tried to find the correct issue number, however it was not as easy as expected:
It either is #80004 or #79718.

[JelleZijlstra]

Possibly the intention is that if you feel the need to set _USE_VFORK to false, you should open a CPython issue and reference it in a comment. However, in that case it's better to be explicit and add a sentence to the docs that says you should open a CPython issue in that case.

[hugovk]

Using git blame (https://github.com/python/cpython/blame/main/Doc/library/subprocess.rst), we can see this was added in PR #91490.

[ronaldoussoren]

The end of that section already states:

Please file issues any time you have to use these private knobs with a way to reproduce the issue you were seeing. Link to that issue from a comment in your code.