Also, fix fetch_languages.py so it can run on python3.

languages.py can change, so users may query on a language that is not
on the list anymore, even if it is still recognized by a few engines.

also made no and nb the same because they seem to return the same,
though most engines will only support one or the other.

and refactor method to make it testable without making requests

utils/fetch_languages.py gets languages supported by each engine and
generates engines_languages.json with each engine's supported language.

TODO: implement image engine