It's been driving me crazy since the last VM upgrade before that version this never happened....
If you have...
session optional pam_mail.so standard
set in /etc/pam.d/su the MySQL dump will fail during the scheduled backups and setting it back to the default fixes that and that shouldn't be the case..
session optional pam_mail.so nopen
the standard switch reports mail in a su login whereas the nopen mutes that.
This needs to be fixed so it works like it did in the past.
BTW this is a BLOCKER bug because all backups fail when this setting is used.