this is very misleading and very error prompt. Mojito that this known limitation that whenever you plan to use a lang bundle, you need to call `Y.Intl.setLang()`, but doing what you're doing in line 55 is going to be problematic.

I have few recommendations for this:

* you should rely on `Y.Intl.lookupBestLang()` (http://yuilibrary.com/yui/docs/api/classes/Intl.html#method_lookupBestLang), and `Y.Intl.getAvailableLangs()` to avoid calling `setLang()` with an invalid lang.

* if the issue is to avoid having bundles that do not contain the right lang information, then you could do completion of the bundles and messages in bundles during build process to guarantee that all bundles and all language are available for use. this is the same we do in flickr and media, and it reduce the complexity of the app code and the framework code drastically in favor of a more normalized build process.