Automated deploys should have a means to alert humans if something is wrong. l10nupdate currently does not other than a "failed" message in the SAL entry. This has been a problem in the past where l10nupdate was not completing successfully for more than a week yet no one noticed nor reported the issue. It wasn't until @greg noticed via his Twitter feed (where he subscribes to @wikimediatech) at the time of the failure.
An Icinga (or otherwise) alert based on the exit status of the l10nupdate run is needed.