There doesn't seem to be a way to retrieve response data for when a connection fails

In the app that I'm developing, on connection fail I need a way to access the response data to know what error message to display.  

This is my addition to the library to bypass the issue.  Alternatively if there exist a way to do so in the current version, would be great if you can point me in the right direction.  Appreciate it!

In this case you should reference the old error in the userInfo with `NSUnderlyingErrorKey`.