I can’t start thesql8.0 on ubuntu 20.04

I install mysql8.0, its fine.
but i want change Data Directory to a New Location.
It's follow this link
https://www.digitalocean.com/community/tutorials/how-to-move-a-mysql-data-directory-to-a-new-location-on-ubuntu-20-04

and follow step4，I can't restart Mysql

Now it’s time to start MySQL. If you do, however, you’ll run into another error. Instead of an AppArmor issue, this error is caused by mysql-systemd-start, a script that supports managing MySQL through systemd. You can inspect this script with the following command:

nano /usr/share/mysql/mysql-systemd-start

and it's out

verify_ready $1
    verify_database $1

    /lib/apparmor/profile-load usr.sbin.mysqld

    if [ ! -r /etc/mysql/my.cnf ]; then
            echo "MySQL configuration not found at /etc/mysql/my.cnf. Please install one."
            exit 1
    fi

So, how can fix this problem? and i don't want reinstall mysql, because i want change Data Directory to a New Location.
Thanks all