var errs error
	var reader io.ReadCloser
	warningsByFilename := map[string]validation.Warning{}

	processFile := func(path string) {
		var err error
		if path == "-" {
			reader = io.NopCloser(os.Stdin)
		} else {
			reader, err = os.Open(path)
			if err != nil {
				errs = multierror.Append(errs, fmt.Errorf("cannot read file %q: %v", path, err))
				return
			}
		}