Impossible to reinstall python-opensync which made unusable my package installation tools

[Cassian Braconnier]

Hi,
Recently, I decided to install a package for
python-opensync
on my Ubuntu 9.04 (Jaunty).

This package was here :
http://www.progweb.com/modules/blackberry/opensync/
(I was said later that this package was for Debian SID)

This was a very bad idea : it completely broke Synaptic, and made it
impossible to install any (other, non python) package with apt-get or
dpkg commands.

Any attempt to remove or reinstall python-opensync with dpkg or apt-get
commands, used with various 'force' options, gave no result, for instance :

=============
root at tux-laptop# dpkg -P --force-remove-reinstreq python-opensync

dpkg - avertissement, problème contourné à cause de --force :
Le paquet est dans un état incohérent - vous devriez
le réinstaller avant d'essayer de le supprimer.
(Lecture de la base de données... 236922 fichiers et répertoires déjà 
installés.)
Suppression de python-opensync ...
Usage: update-python-modules [-v] [-c] package_directory [...]
       update-python-modules [-v] [-c] package.dirs [...]
       update-python-modules [-v] [-a|-f|-p]

update-python-modules: error: 
/usr/share/python-support/python-opensync.public is not a directory
dpkg : erreur de traitement de python-opensync (--purge) :
le sous-processus pre-removal script a retourné une erreur de sortie 
d'état 2
Usage: update-python-modules [-v] [-c] package_directory [...]
       update-python-modules [-v] [-c] package.dirs [...]
       update-python-modules [-v] [-a|-f|-p]

update-python-modules: error: 
/usr/share/python-support/python-opensync.public is not a directory
dpkg : erreur lors du nettoyage :
le sous-processus post-installation script a retourné une erreur de 
sortie d'état 2
Des erreurs ont été rencontrées pendant l'exécution :
	python-opensync

====================


The pre and post removal scripts are respectively :

/var/lib/dpkg/info/python-opensync.prerm :


=================

#!/bin/sh
set -e
# Automatically added by dh_pysupport
if which update-python-modules >/dev/null 2>&1; then
    update-python-modules -c  python-opensync.public
fi
# End automatically added section

=========================


/var/lib/dpkg/info/python-opensync.postinst :


==================

#!/bin/sh
set -e
# Automatically added by dh_pysupport
if which update-python-modules >/dev/null 2>&1; then
    update-python-modules  python-opensync.public
fi
# End automatically added section

==========================

For the time being I cannot install anything using dpkg or apt-get (nor 
synaptic) : I get an error message saying
that "python-opensync should be reinstalled but that its archive is 
unavailable", and as I said, any attempt to reinstall python-opensync fails.

So far I could not get any useful advice on the french ubuntu users 
forum, it is the reason why, though I am in no way a python-guy,
I turned to this list.

Thank you for any advice.
Idoin