Go with the exception's own 'message' in the verify_credentials method.

 A 401 exception can be returned by the WinRM service on the SCVMM box for reasons other than a user has entered invalid credentials. For example, if we set the winrm/config/service/AllowUnencrypted value to 'false' we get the same 401 error, probably because it is still a denial of access..
I think it is safer just to stick with the message built into the exception. That said, I am open to appending some clues to the message such as "Check credentials and WinRM configuration settings"… or something like that.

https://bugzilla.redhat.com/show_bug.cgi?id=1131236