[3.5] closes bpo-38576: Disallow control characters in hostnames in h… by tapakund · Pull Request #19300 · python/cpython

There's some sort of ongoing communication problem between Travis CI and Github. It doesn't happen frequently, so if you just re-run the Travis CI check it'll usually work fine the second time. By merging a different PR, that caused this PR to be out-of-date, and updating it meant I could run Travis CI again, and now everything is fine.