do not purge userdir-ldap on upgrade (!)

howto/upgrades/bullseye.md

@@ -131,9 +131,9 @@ bullseye procedure.
 
         apt purge $(dpkg -l | awk '/^rc/ { print $2 }') # purge removed packages
         apt autoremove -y --purge
-        apt purge $(deborphan --guess-dummy)
+        apt purge $(deborphan --guess-dummy | grep -v python-is-python2)
         dsa-check-packages | tr -d ,
-        while deborphan -n | grep -q . ; do apt purge $(deborphan -n); done
+        while deborphan -n | grep -v python-is-python2 | grep -q . ; do apt purge $(deborphan -n | grep -v python-is-python2); done
         apt autoremove -y --purge
         apt clean
         # review and purge older kernel if the new one boots properly