The problem for me was that the file /etc/apparmor.d/local/usr.sbin.mysqld did not exist after the upgrade. I manually copied one from one of the empty ones (i.e. only had header comment) and then everything was good to go.
The problem for me was that the file /etc/apparmor. d/local/ usr.sbin. mysqld did not exist after the upgrade. I manually copied one from one of the empty ones (i.e. only had header comment) and then everything was good to go.