I believe the IOError message is because of the print statement and it having nowhere to write. There are quite a few occurrences of this on errors.ubuntu.com, however they are not grouped together because the tmp folder from which the upgrade is ran is different. Here is one example though:
https://errors.ubuntu.com/oops/23b13516-9e1c-11e2-a76a-e4115b0f8a4a -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1069745 Title: update-manager fatal error while upgrading from precise to quantal, caused by PPA To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1069745/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
