[Cantor] Python back-end interpreter path

[Marcello Massaro]

Hi Alexander,

> This is not possible right now. We've got a similar/same request already a
> couple of times. I'm looking into this right now.

That's a shame, but nice to know that it's on the todo list. :)

> You mentioned three python runtimes installed on your system. Which one is
> used by Cantor? The one installed "by the system"?

I'm on openSUSE Tumbleweed. In my PATH normally I have python (2.7), 
python3 (3.8.10), and python3.9 (3.9.5). Those are the commands names in 
/usr/bin.

If I open a clean Cantor worksheet, with "Python" set as default 
backend, the output of sys.version is 3.8.10. I assume Cantor simply 
resolves/uses /usr/bin/python3 then.

Cheers,
Marcello