code: def get_host_ip(self, env_with_dig='ingi/inginious-c-default'):
          
          try:
              container = self._docker.containers.create(env_with_dig, command="dig +short myip.opendns.com @resolver1.opendns.com")
              container.start()
              response = container.wait()
              assert response["StatusCode"] == 0 if isinstance(response, dict) else response == 0
              answer = container.logs(stdout=True, stderr=False).decode('utf8').strip()
              container.remove(v=True, link=False, force=True)
              return answer
          except:
              return None
docs: Get the external IP of the host of the docker daemon. Uses OpenDNS internally.
          :param env_with_dig: any container image that has dig