class Cucumber::Formatter::MessageBuilder

def on_gherkin_source_read(event)
  message = Cucumber::Messages::Envelope.new(
    source: Cucumber::Messages::Source.new(
      uri: event.path,
      data: event.body,
      media_type: 'text/x.cucumber.gherkin+plain'
    )
  )
  output_envelope(message)
end