| 
Packages that leave obsolete conffiles after upgrade.
Using  dpkg-maintscript-helper rm_conffilevia dh_installdeb package.maintscript files is the recommended way to clean them up.
There may be false positives, e.g. if a conffile was converted to a maintainer script managed configuration file. The commandline to find these logs is:  
COMMAND='grep -E "OBSOLETE CONFFILE"'
 |