and I get the same result with the python:3.6.7 image docker

> docker run --rm -v $PWD:/src -it python:3.6.7 python /src/demo.py
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/urllib/request.py", line 1318, in do_open
    encode_chunked=req.has_header('Transfer-encoding'))
  ...
  File "/usr/local/lib/python3.6/socket.py", line 713, in create_connection
    sock.connect(sa)
ConnectionRefusedError: [Errno 111] Connection refused

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/src/demo.py", line 12, in <module>
    response = urllib.request.urlopen(req)
  ...
  File "/usr/local/lib/python3.6/urllib/request.py", line 1320, in do_open
    raise URLError(err)
urllib.error.URLError: <urlopen error [Errno 111] Connection refused>

I am really sorry but I can't reproduce your issue.

What is your Linux distribution or OS?

Thank you