When translation packages are missing, the KCM shows a message saying, "There are no additional languages available on this system." This is nice. However it's not immediately obvious how to resolve this. Presumably some language packages are missing, but the user has no idea what they are. The InlineMessage that shows this text should have a button that downloads the missing language packages using PackageKit when clicked, so the user can fix the problem themselves rather than being confused and frustrated.
*** This bug has been marked as a duplicate of bug 366328 ***