This works for me, YMMV
$ sudo chown _apt:root /var/lib/update-notifier/package-data-downloads/partial/
$ sudo rm /var/lib/update-notifier/package-data-downloads/partial/*.FAILED
$ sudo apt install --reinstall update-notifier-common
This works for me, YMMV
$ sudo chown _apt:root /var/lib/ update- notifier/ package- data-downloads/ partial/
$ sudo rm /var/lib/ update- notifier/ package- data-downloads/ partial/ *.FAILED
$ sudo apt install --reinstall update- notifier- common