Comment by jeroenhd

This is new:

    $ sudo apt upgrade
    Reading package lists... Done
    Building dependency tree
    Reading state information... Done
    Calculating upgrade... Done
    Try Ubuntu Pro beta with a free personal subscription on up to 5 machines.
    Learn more at https://ubuntu.com/pro
    0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded
    $ 

This removes the spam and hopefully prevents this issue from showing up again:

    sudo ln -s /dev/null /etc/apt/apt.conf.d/20apt-esm-hook.conf

Can't wait for these ads to show up in the cron emails from my automated upgrade scripts. I know apt doesn't have a stable console output but I shouldn't need to defend against ads in the output.