Print errors to stderr, don't crash the app
Print errors to stderr, don't crash the app

- print out the guilty file, which is useful
- continue to format other files if possible
- suggest where to report the issue

christofferqa/dart_style,alechenninger/dart_style,mark-henry/dart_style,dart-lang/dart_style,christofferqa/dart_style,alechenninger/dart_style,mark-henry/dart_style