I am pretty certain this is not a common thing, and I will investigate more as to why I need apparmor, but while working on a Linux Mint 18 box today, it would not print. In fact CUPS kept crashing.
audit: type=1400 audit(1500298990.659:144): apparmor="DENIED" operation="open" profile="/usr/sbin/cupsd" name="/home/.ecryptfs/number9/.ecryptfs/wrapped-passphrase" pid=1265 comm="cupsd" requested_mask="r" denied_mask="r" fsuid=1000 ouid=1000
A little investigating lead to:
sudo aa-disable /etc/apparmor.d/usr.sbin.cupsd
That code was taken from: this bug report.
and a restart of cups, and it works.
Now, off to read about why I need apparmor.