Handle failure better in PhaseCallRunner#run

Maybe things were different in Maven 2. At any rate, if a Mojo throws an exception, the PhaseCallRunner was swallowing it. Passing `-e` / `-X` flags to mvn does not help.

Ideally the PhaseCallRunner would respect `-e` (maybe that shows up in the `MavenSession` somewhere?) when logging build failure exceptions. I've erred on the side of actually logging something useful in this case ;)