add these three lines

staged_messages_controller.rb

  def check_contents
    @staged_message = StagedMessage.new params[:staged_message]

    @staged_message.hl7_message ||= request.body.read.chomp

    puts "CONTENT_TYPE=#{request.env['CONTENT_TYPE']}" # <<<< line 183
    puts "Content-Type=#{request['Content-Type']}"     # <<<<
    puts "format=#{request.format}"                    # <<<<