Comment 14 for bug 1637801

> The correct approach is to have gettext look into the langpack translations first, and then fall back to the package's translations.

No, it's not. Normal/released Ubuntu packages get their translations stripped out of the debs. But if you install a backport, third-party package, or self-built package, you want to see the translation that it ships, not the Ubuntu translations as they now apply to an older version only. Hence /usr/share/locale/ must have precedence over /usr/share/locale-langpack/.

There are just a handful of packages which you need for upgrading and *installing* langpacks which have their translations built-in, like apt or language-selector.