to remove old kernels (excluding the running one)

do not do anything if we failed to detect the running one (ie:
chroot))

meant to update the mirror list

To make it possible to associate more metainformation with the media
stored in urpmi.cfg, we need to be able to associate a given urpmi.cfg
medium with the media.cfg files it was created from. To do that, we save
media.cfg files locally in /etc/urpmi/mediacfg.d/$name with an
additional 'url' or 'mirrorlist' files. Those files are used to resolve
the relative names stored in media.cfg so that we can associate them
with the absolute names stored in urpmi.cfg. The mediacfg.d dir is
cleaned up when a medium is removed (if necessary).

rationale: all prints in transaction/installation code now go through
a callback that redirects the output at install time