With plesk sbin pum --check
or
apt-get update && apt-get upgrade -y
I get this error
2018-03-06 13:14:07 INFO: pum is called with arguments: ['--check']
2018-03-06 13:14:13 ERROR: W:The repository 'http://ppa.launchpad.net/canonical-kernel-team/pti/ubuntu xenial Release' does not have a...