Definitely on the right track, but how do I get the error message?  And, from your example, what is ui.message?  In my test, it always returns "The remote request to fetch data has failed: (error) undefined", no matter what kind of error happens on the server.  I'm testing by throwing a standard c# exception with a sample message "Database timeout, please try again" for now.  I don't see that in either evt or ui properties.