In my case, it was not due to any internet connection failure - the system was missing some updates.
I should have run the update before upgrading to the next version, but I forgot to do that in that instance. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/687542 Title: Update-manager does not restore original sources.list when upgrade fails -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
