title: Python Docker Container gets ProxyError, despite I can connect to Server manually
body: <p>Really weird problem here. I have a Python Application running inside a Docker Container which makes requests in  different threads to a http restapi. When I run the Container, I get the error:<br />
  <code>ERROR - host not reachable abc on thread abc. Stopping thread because of HTTPConnectionPool(host='corporate.proxy.com', port=111111): Max retries exceeded with url: http://abc:8080/xyz (Caused by ProxyError('Cannot connect to proxy.', RemoteDisconnected('Remote end closed connection without response')))</code></p>
  <p>When I log in onto the docker host and make the request with curl, then it works.
  When I execute the request inside the docker container (docker exec ....), then it works.
  When I start the python interpreter inside the container and make the request with the requests module (like application does it), then it works.</p>
  <p>The Container is attached to the host network of the docker host machine</p>
  <p>Did anyone had also an issue like this?</p>