Comment 23 for bug 396414

I discussed that with Michael again, and writing this as an aptdaemon plugin is a lot more elegant than modifying the core aptdaemon code, so moving this to language-selector.

As for performance, I now rewrote the check-language-support logic from scratch, as the l-s code was really horrible, slow, and hard to maintain. The replacement is much smaller, (IMHO) easy to read and understand, has full test coverage, and is fast.

I added a performance test to the test suite which does a full check of all missing lang support packs for all installed packages for all installed locales, and it takes a mere 8 ms on my system (under the condition that we have an initialized apt.Cache() object, which is given in an aptdaemon plugin). I think this is a negligible overhead and well worth spending.