Thanks for the review Martin.

> However I understand Rolf specifically wanted chunked encoding to work with the existing urlopen() framework, at least after constructing a separate opener object. I think that should be practical with the existing HTTPConnection implementation.

The original issue was that http.client doesn't support chunked encoding. With this patch, chunked encoding should more or less come for free with urlopen. There's absolutely no reason as to why HTTPConnection should not support transfer encoding out of the box given it's part of the HTTP1.1 spec. I do understand that there are some modifications needed in urllib.request in order to support the changes here, but I didn't include those in the patch as to not conflate the patch. I think that it's also reasonable to open a new issue to address the feature in urllib.request rather than piggy-backing on this one.