I have run the minimal example provided on both Python2 and Python3 with the same results. Sorry if that was not clear.

I did look at issue 1424152 but it seemed to me that I was experiencing a different problem.

When I try and open the page, I get a squid error page with a somewhat vague error saying that "the method is not supported" (even though it's a simple GET and I can get the same page with other tools like wget or a web browser). Unfortunately, I don't have access to the proxied environment right now, and I will need to ask for the squid logs anyway since I can't access them.

I have to say that I have experienced this problem while using buildout as zc.buildout.download uses urllib.urlretrieve. Surprisingly, it succeeds on Python3, but it fails with Python2 which is our supported version (so there's currently no way that I can use Python3 at work).