I got this bug trying to download the linux source, fixed it with the following line (which was posted in this bug's duplicate thread):
sudo chown _apt /var/lib/update-notifier/package-data-downloads/partial/
I got this bug trying to download the linux source, fixed it with the following line (which was posted in this bug's duplicate thread):
sudo chown _apt /var/lib/ update- notifier/ package- data-downloads/ partial/