The problem is the blender PPA you have enabled. It provides python packages greater than the ones in Trusty and the release upgrader will not downgrade packages.
libpython3.4 3.4.0-2ubuntu1irie1~quantal1 0 libpython3.4-minimal 3.4.0-2ubuntu1irie1~quantal1 1 libpython3.4-stdlib 3.4.0-2ubuntu1irie1~quantal1 1 You'll need to use the ppa-purge tool to remove the blender PPA. ** Changed in: ubuntu-release-upgrader (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1365076 Title: do-release-upgrade fails from 13.10 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1365076/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs