I have managed to bypass this problem by manipulation the Python code of the upgrade process. But it is far easier to bypass it properly by setting up a config file in /etc/update-manager/release- upgrades.d/*.cfg.
According to http://askubuntu.com/questions/425355/error-authenticating- some-packages-while-upgrade one needs to create a file /etc/update- manager/release-upgrades.d/unauth.cfg with the contents: [Distro] AllowUnauthenticated=yes The upgrade runs smoothly through. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1550922 Title: dist-upgrade from Ubuntu Mate 14.04.4 LTS to 16.04 LTS (Beta1) fails To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1550922/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
