test_urllib2_localnet is concerned with testing connections only using 'localhost' or '127.0.0.1' hosts. If a user has the "http_proxy" environment variable set, these test will likely fail as the proxy won't have any idea where to send a request for 'localhost'. Patch makes urllib.request.urlopen ignore proxies set in the environment. Note that this only works for http proxies. https proxies are trickier and require more work.
Jeff, Thanks for raising this issue. The aspect of skipping localhost for proxies in urllib2_localnet tests can be handled in a different way as well, namely by setting the environment varible NO_PROXY to "*". By this the skip_proxies in urllib2 returns True and proxies are skipped for both HTTP and HTTPS.