Comment 3 for bug 1822780

I don't think xenial is affected, probably due to a bug. The requires.txt file in xenial's python3-pymacaroons package is empty:

root@xenial:~# apt-cache policy python3-pymacaroons
python3-pymacaroons:
  Installed: 0.9.2-0ubuntu1
  Candidate: 0.9.2-0ubuntu1
  Version table:
 *** 0.9.2-0ubuntu1 500
        500 http://br.archive.ubuntu.com/ubuntu xenial-updates/universe amd64 Packages
        100 /var/lib/dpkg/status
root@xenial:~# dpkg -L python3-pymacaroons|grep requires.txt
/usr/lib/python3/dist-packages/pymacaroons-0.9.2.egg-info/requires.txt
root@xenial:~# cat /usr/lib/python3/dist-packages/pymacaroons-0.9.2.egg-info/requires.txt
root@xenial:~# l /usr/lib/python3/dist-packages/pymacaroons-0.9.2.egg-info/requires.txt
-rw-r--r-- 1 root root 0 Jun 3 2016 /usr/lib/python3/dist-packages/pymacaroons-0.9.2.egg-info/requires.txt
root@xenial:~#

root@xenial:~# python3 -c "__requires__ = 'pymacaroons';from pkg_resources import load_entry_point"
root@xenial:~#

And ua works fine:
root@xenial:~# ua
usage: ubuntu-advantage [command] [flags]
Try 'ubuntu-advantage --help' for more information.
root@xenial:~# apt-cache policy ubuntu-advantage-tools
ubuntu-advantage-tools:
  Installed: 19.1-0ubuntu1~361~git.6bb6fcc~ubuntu16.04.1
  Candidate: 19.1-0ubuntu1~361~git.6bb6fcc~ubuntu16.04.1
  Version table:
 *** 19.1-0ubuntu1~361~git.6bb6fcc~ubuntu16.04.1 500
        500 http://ppa.launchpad.net/canonical-server/ua-client-daily/ubuntu xenial/main amd64 Packages
        100 /var/lib/dpkg/status
     10ubuntu0.16.04.1 500
        500 http://br.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages