[PySide] Multiple PySide for Multiple Qt in a same python install?

[Olivier B.]

I am preparing to build an new Qt version. So i will build a new
PySide2 with it. So the problem will happen of having multiple PySide
versions useable in python depending on the Qt i want to use.
The Python install also has a matplotlib module, which uses PySide2 as backend

I did not manage to install PySide2 outside of python
site-packages/PySide2 using setup.py, so i manually move it and use
pth files so each PySide version will have its own storage folder.

But then, i would like that python loads the proper PySide depending
on the current Qt i choose to use.
I have a QT_VERSION environment variable during python sessions. I
could maybe add a different site dir in PySide's sitecustomize.py that
i created, that depends on that QT_VERSION

What means do you people have in place to switch Qt/PySide2 versions?