I tried to reproduce the problem on an unpatched Xenial machine but couldn't as it seems that /usr/lib/ubuntu-release-upgrader/check-new-release (from comment #10) doesn't use HTTPS to get to changelogs.ubuntu.com. If someone has clear steps to reproduce on Xenial, I'll be happy to try it out.
I tried to reproduce the problem on an unpatched Xenial machine but couldn't as it seems that /usr/lib/ ubuntu- release- upgrader/ check-new- release (from comment #10) doesn't use HTTPS to get to changelogs. ubuntu. com. If someone has clear steps to reproduce on Xenial, I'll be happy to try it out.