Installing update notifier fixed the problem for me in Ubuntu-MATE 18.04 LTS. Code: `$ sudo apt-get install update-notifier`
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1690475 Title: TypeError: 'NoneType' object is not callable To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1690475/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
