Python selection on installers

On the installers dialog screen for selecting a Python executable there is no information about the minimum version supported.

The error message also does not provide clear indication of the problem.

The user has to the read the documentation to understand that SNAP only supports Python from v3.9 to v3.12.

Knowing the reluctance of users to RTFM, this will certainly lead to complaints on the forum that SNAP does not work with Python.

So, please:

1. Add clear and succint information to the dialog screen.

2. Provide relevant error messages.