How to upgrade a Python minor version, eg 3.8.x -> 3.9.x?

[Nuc1eoN]

What is the proper way to update a Python minor version, like 3.8.x to 3.9.x?

My steps are like this:

NewVersion Python 3.9.20
[...]
Compile Python 3.9.20

It compiles and installs fine. With this exception:

SymlinkProgram: Conflict: /System/Aliens/PIP/3.8/bin/pip3

python3 --version correctly shows Python 3.9.20.

But upon trying to install a meson recipe, eg Mesa, I am getting:

Compile: This is a meson type recipe and you don't seem to have meson installed.

This seems to be due to Alien (since meson is installed via PIP3/Aliens). So I am trying to reinstall meson:

Alien --install PIP3:meson

This works actually:

which meson
/System/Aliens/PIP/3.9/bin/meson

However I still cannot compile meson recipes.
Compile would still not find meson!

Also upon re-running Alien --install PIP3:meson I am getting:

Requirement already satisfied: meson in /System/Aliens/PIP/3.8/lib/python3.8/site-packages (1.5.2)

which is referencing python 3.8 again (?).

To make it more complicated under the /System/Aliens/PIP/3.9/lib/ subfolder (note: 3.9!!) we are getting python3.8/site-packages again. Full path:

/System/Aliens/PIP/3.9/lib/python3.8/site-packages

It seems Aliens/PIP3(?) has to be updated to work with the new python minor?

However, if I understand the python recipe and its Alien compatibility patch correctly, Aliens should actually re-use the packages installed under Python3.8 with PIP3:

We let a program to import modules from older Python versions that share the same major number.

This does not seem to work though?!
(I did update PYTHON_MINOR=7 to PYTHON_MINOR=9 in the patch btw)

---

Further, I wanted to make meson recipes Compile again, so I did a

SymlinkProgram Python 3.8.1

This did not fix the problem, still getting:
"This is a meson type recipe and you don't seem to have meson installed."

The only way to "fix' it was to

RemoveProgram Python 3.9.20

in the terminal.

I was not brave enough to do it the other way around and delete Python 3.8.1 to see if that would make it work 😅

I'd be grateful for any help or pointers!

PS: Python >= 3.9 is actually required to successfully build Mesa nowadays. So that is why I am trying to update python in the first place.