title: docker-py exec_start howto stream the output to stdout
body: <p>I'm trying to execute some long processes with docker-py
  My problem is that I'm not able to see the output of what I'm doing...</p>
  
  <p>How can I stream the output from the docker exec directly to stdout ? or better to logging ?</p>
  
  <p>I've seen there is a "stream" parameter, but I don't undestand how to use the generator returned...</p>
  
  <pre><code>        exec_c=self.docker.exec_create(myContainer,e["cmd"])
          output=self.docker.exec_start(exec_c)
          self.logger.info(output)
  </code></pre>
  
  <p><a href="http://docker-py.readthedocs.org/en/latest/api/?highlight=exec#exec_create" rel="nofollow">http://docker-py.readthedocs.org/en/latest/api/?highlight=exec#exec_create</a></p>