title: Kafka simple producer not sending messages and not giving an error
body: <p>I am writing a simple producer i just want to send raw data into a topic. for some reason i need to specify serialiser that will convert the message to json then to utf-8 then send in a json message.. </p>
  
  <p>this code doesn't work (no error but nothing to consume in the topic)</p>
  
  <pre><code>from kafka import KafkaProducer
  
  producer = KafkaProducer(bootstrap_servers=['localhost:9092'])
  topic = "my_new_topic5"
  
  producer.send(topic, b'test message')
  </code></pre>
  
  <p>this code works </p>
  
  <pre><code>producer = KafkaProducer(bootstrap_servers=['localhost:9092'],
                       value_serializer=lambda x:
                       dumps(x).encode('utf-8'))
  
  for e in range(2):
      data = {'number': e}
      producer.send('numtest', value=data)
      sleep(5)
  </code></pre>