Unsetting is_imported translations doesn't work from uploads

[Данило Шеган]

When there is an existing imported translation (packaged/upstream), it's impossible to override it with an empty imported translation in the future.

This usually happens if a someone had inadvertently copied a different language PO file to another one in a package without being properly cleaned up (at least, this is the only few cases I've encountered so far).

However, more important might be cases where maintainers fix translations so programs don't crash (i.e. C format strings and similar), when they usually just mark the string as fuzzy (which is equivalent of empty in LP).

[Данило Шеган (danilo)]

Btw, we should note that this was an intentional design choice in early days so we keep at least one good translation (assumption was that whatever is coming from a package is good). Maybe we should revisit it.

[Данило Шеган (danilo)]

Changing this with message sharing would cause more problems than solve (i.e. older untranslated release might get a half-empty translation imported, and then that would unset newer fully translated one as well). We won't do it.