I was responsible for the previous iteration, too.  I don't remember before that (fail silently?) but I do remember wondering if people want to see a stack trace about a missing class, that says "ClassNotFound".  By people, I mean the guy who takes up support for continuations plugin and can't get the class path right in sbt, or whatever.  In Plugins, it recover[Any]s and just uses the message, which would include the causative message IIUC.