Adds checking for the word 'unauthorized' to the unauthorized check. #171

Looking at the error message I've been having, ` failed with error "unauthorized"` and then looking at errors.rb, `#error_message` it seems like there was neither a code nor an assertionCode in the response.

As such, I decided to regex the error message for the word unauthorized. A bit shady perhaps, but I'm getting this error frequently and sporadically in production and staging after upgrading to 2.4.1. :-\