This is because you are using a version of python-apt-common which is not from the official Ubuntu archive and likely does not ship the file /usr/share/python-apt/templates/Ubuntu.info.
python-apt-common 2.1.2pop0~1587756471~20.04~cd2988e [origin: unknown] -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1900440 Title: Upgrade to 20.10 fails To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1900440/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
