Did you want to run the update checker and get stopped dead?
mysqlsh --mysql -u root -h localhost -P 3306 --database=somedatabase MySQL Error 1698 (28000): Access denied for user 'root'@'localhost'
If your root user is using an auth type other than "mysql_native_password",
You might have better luck adding a user with the correct PRIV and auth user type.
Hint: If you use Debian / Ubuntu, you can use the debian-sys-maint user
Search for debian-sys-maint for info on where to find the password for that user / reset it.
Plow ahead with:
util.checkForServerUpgrade();