This way stolen from `addons.models` ; please refactor that code and add this utility method in the `translations` app instead of copying it.

Also, there is an alternative, using `translations.models.delete_translation()` but that only works on a specific translation, not all of them. it deletes all the rows instead of NULLifying them though, which is nice. I'd love for us to use that instead, but might be better in a separate bug.