Ensure Tails installer is removed from Debian & Ubuntu by the end of 2019

• upload the changes from #16011 (closed) to sid, stretch-backports and Ubuntu PPA; see the plan on #16011-note_6 for detailed timing info

Then:

• late February: get Tails Installer removed from testing via a RC bug that’ll trigger the auto-removal process at some point during the Buster freeze; don’t do that earlier because we might need to get some follow-up fixes into stretch-backports if we messed it up, and we can’t do that anymore once the package is removed from testing
• at the end of 2019:
  • drop from Debian sid → submitted removal request to ftpmasters for unstable, see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=942790
  • → I did not request removal from stretch-bpo.
  • drop from Ubuntu PPA → done on Oct 21st 2019
    → write email to help desk in case users complain
  • adjust our release process / packaging doc → done in feature/16012-remove-tails-installer → merged to master so that nobody tries to commit to salsa, as the repo is now read-only.
  • adjust Vcs-control fields → done in tails-installer.git: 9122a5408f4804a61ef0966ba63bd8b97713cbad
  • archive the repository on salsa.d.o → no commits are possible anymore.
  • keep old branches for reference in the packaging repo → if the upstream developers want to change this, they can do that and refer to the archived version on https://salsa.debian.org/pkg-privacy-team/tails-installer
    (this is part of core work in Debian)

Feature Branch: master

Parent Task: #15292 (closed)

Related issues

• Blocked by #16011 (closed)

Original created by @u on 16012 (Redmine)