Script to diagnose "no module named yum"

Since this is still happening, and is a FAQ but is not addressed
on the Yum FAQ page, I would be interested if anyone has a script
which examines current settings to determine *why* in any instance
this error can still occur.

>From much searching it looks as if it's a broken/inconsistent Python
installation, but Python itself does not appear to provide the means
to diagnose or fix this. (FWIW I think it should !)

It's not sufficient (as many of the "answers" suggest) to reinstall
from source or from RPM - or from Synaptic.
This does not seem to fix whatever it is that is out of alignment,
since I have reinstalled Python, pygtk and yum from source
without any improvement.

I would be very grateful if the yum shell script would be able
to take a more proactive approach to finding out what it
needed and what was missing - maybe looking in both
/usr/lib and /usr/local/lib for example, or finding multiple
Python installations and behaving in a sensible way.

(I once used a LAMP-package installer which did a very good job of
telling you which bits were working and what seemed incorrect)

I realise that if everything is set up correctly, "things just work"
but especially if you are installing packages and upgrades,
that might not be the actual situation.

Many thanks,
MikeW