I begin to think the problem WAS NOT with validate_nice_value, but rather with the priority of debconf. "sudo dpkg-reconfigure --force -plow x11-common" seems to work but "sudo dpkg-reconfigure --force -pmedium x11-common" seems to bug.
-- x11-common have an important debconf bug https://launchpad.net/bugs/68267 -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
