Right now those generate the unable to connect error page. I agree with the other comments above. There are possible errors that wouldn't have their own specific language. 

There is a default gecko error message that is provided. It's likely that we'd want to display that message along with a generic title like 'Unable to connect'. Figuring out the details there with UX is likely to take a little bit of time and these changes are a great start and will enable whatever UX wants to do.