Updating thunderbird from 68 to 78 in focal

[Olivier Tilloy]

Hello,

I am working on updating thunderbird in focal from version 68 to
version 78 (78.5.0 is currently in focal-proposed), because upstream
has ended support for the 68 series (bionic will follow).
This is a new major version that brings a number of changes, and
breaks a couple of packages in the archive (jsunit and tinyjsd, see
https://bugs.launchpad.net/ubuntu/+source/thunderbird/+bug/1895643/comments/29
for details). I have consequently marked thunderbird as breaking these
packages to ensure they are uninstalled on upgrade, and I have started
a conversation with the SRU team (Robie specifically, who suggested
this is TB territory) to try and come up with an optimal solution. Are
there precedents of similar situations?
Should tinyjsd and jsunit be removed from the focal archive? Should we
prepare SRUs making them empty (Robie mentioned this was done with
bitcoin and similar)?
How do we mitigate and document the breakage?

Thanks,

 Olivier