this misfunction was picked up by xymon/apt, which comainted that the Last apt update was too old
This regression was introduced in commit [29ce88975f], which replaced the unattended upgrade mechanism with the cluster cron based autoupdate mechanism (but only for alambix clustern, for some reason)
The bug in the cluster cron based autoupdate system was caused by the fact that the code forgot to update the package list before calling apt list --upgradable. As a result, the package list was never updated on alambix, and therefore scurity updates were never seen. This problem was not present on physix, which does still have the unattended upgrade mechansim along with the cluster cron based autoupdate system.
fixes [https://bugzilla.ipr.univ-rennes.fr/show_bug.cgi?id=3810]