class RuboCop::Formatter::FormatterSet

def add_formatter(formatter_type, output_path = nil)
  if output_path
    dir_path = File.dirname(output_path)
    FileUtils.mkdir_p(dir_path)
    output = File.open(output_path, 'w')
  else
    output = $stdout
  end
  self << formatter_class(formatter_type).new(output, @options)
end