Comment 3 for bug 775691

Ok, so here's my assesment of the issue:
 - the core functionality actually works (bar an edge case, see below)
 - migration was probably never done for direction ubuntu -> upstream; I can understand how this was skipped because one would have to check if the ubuntu translation reviewer is allowed to edit the upstream translation as well before setting it as current upstream as well; I doubt there are any definite plans to do this migration.

Solution to the migration problem is to download all the PO files from Ubuntu and re-upload them on the project (or if they are already in the source tree, just 'request one time import').

Corner case that'd still need fixing:
 - I got confused before reading the code about the severity, because the code is not checking for the LP permission (launchpad.Edit), so people with launchpad.TranslationsAdmin, even though they can translate anything, are not considered to be able to change the other side too (even though they can). This is a bug, but it affects a minor number of people, and is mostly just confusing (as a TranslationsAdmin, I won't usually translate Catalan, even though I did it on staging for the purposes of testing).

I'll modify the bug to be about this corner case (and lower the priority) instead unless someone objects and feels migration should be done across Launchpad, when we can re-evaluate.