I am using letsencrypt independently from Webmin and have set up a renewal-hook that calls "service webmin restart". This leads to "Pre-loaded WebminCore" being printed out on stderr as it seems, therefore creating mails (from multiple servers) by cron like this:
Error output from restart_services:
Pre-loaded WebminCore
The message doesn't seem like it needs to be on stderr. If so, this could probably be changed to stdout (I obviously don't want to redirect stderr to /dev/null =)). Seems to only affect Debian Wheezy systems.
Yeah, this messages is un-necessary. I'll fix it in the next webmin release.
thx!