Comment 33 for bug 1992026

To be more specific

```
sudo apt dist-upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
Get more security updates through Ubuntu Pro with 'esm-apps' enabled:
  libgraphicsmagick-q16-3 librpmsign8 python2.7-dev rpm2cpio liburiparser1
  libmaven3-core-java libopenexr-dev php-symfony-expression-language
  libgegl-0.4-0 librpmbuild8 lynx-common libzmq5 python2.7-minimal libhdf5-103
  libgegl-common libpython2.7 debugedit python2.7 libpython2.7-dev lynx
  libzmq3-dev phpmyadmin librpmio8 rpm-common maven rpm librpm8
  libhdf5-cpp-103 cpanminus libjs-jquery-ui libopenexr24 libsdl2-2.0-0
  libmysofa1 libpython2.7-minimal php-symfony-cache libgraphicsmagick++-q16-12
  php-symfony-var-exporter libpython2.7-stdlib
Learn more about Ubuntu Pro at https://ubuntu.com/pro
#
# "Phased updates" allow careful rollout of deb package changes at scale.
# You may see these as packages that have been "kept back". Learn more at
# https://ubuntu.com/server/docs/about-apt-upgrade-and-phased-updates
#
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
```

that I just got is a clear ad for Ubuntu Pro, that claims that updates
were deliberately withheld from being available because I am not subscribed
to some product by Canonical.