Needed for I869af06896b9757af18488b916211c5a41a8c563, where I am
trying to change LanguageFactory in MediaWiki core not to use
MWException.
Language::isSupportedLanguage() does not actually throw,
so this sigh can be one of relief.
Change-Id: I3079d8e18d88a4a26c2f2b09dccd4beea06678ee