Track ticket: https://code.djangoproject.com/ticket/19811
Fixed #19811 - Added language code fallback in get_language_info.
This test will surely fail on Python 3 (no u prefix). Either use the str_prefix utility in the test, or simply don't use the %r placeholder in the exception.
If you want I can remove %r from exception message.
Fixed in #791 and bfd4a71.