code: private AssetException rewrite(final AssetException ex) {
      List<StackTraceElement> stacktrace = Lists.newArrayList(ex.getStackTrace());
      List<AssetProblem> problems = ex.getProblems();
      AssetProblem head = problems.get(0);
      stacktrace.add(0,
          new StackTraceElement(head.getFilename(), "", head.getFilename(), head.getLine()));
      ex.setStackTrace(stacktrace.toArray(new StackTraceElement[stacktrace.size()]));
      return ex;
    }
docs: Add a virtual/fake stacktrace element with the offending file, useful for whoops.
  
  @param ex Stack trace to rewrite.
  @return Same exception with new stacktrace.