If you're trying to log into a MySQL 8 box using an old client you may receive the following message:
Authentication plugin 'caching_sha2_password' cannot be loaded
To fix it, you need to make sure that you are using the "old-style" of MySQL passwords.
Log into the box and run:
ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'PASSWORD';
If you receive:
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements
UNINSTALL COMPONENT 'file://component_validate_password';