MariaDB upgrade from MySQL 5.7 fails with "NO_AUTO_CREATE_USER" error.

Symptoms

When trying to upgrade to MariaDB from MySQL 5.7 the following error is presented in WHM's "Home / SQL Services / MySQL / MariaDB Upgrade":

An upgrade on your system is not possible at this time! Please correct the following errors before you attempt to upgrade:
The setting "NO_AUTO_CREATE_USER" is not compatible with MySQL® 8. You must remove it from the "sql_mode" variable in the "/etc/my.cnf" file.

Description

The issue is related to the SQL mode "NO_AUTO_CREATE_USER" enabled within the /etc/my.cnf file:

grep sql_mode /etc/my.cnf
sql_mode="STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"

We've opened an internal case for our development team to investigate this further. For reference, the case number is CPANEL-43218. Follow this article to receive an email notification when a solution is published in the product. 

Workaround

Remove the SQL mode from the /etc/my.cnf file.