@Override
 public String getMessage() {
   StringBuilder fullMessage = new StringBuilder("Compilation failed");
   int i = 1;
   for (Diagnostic<? extends JavaFileObject> diagnostic : diagnostics) {
     fullMessage.append("\n    ").append(i++).append(") ");
     Diagnostics.appendTo(fullMessage, diagnostic, 8);
   }
   return fullMessage.toString();
 }