While I appreciate that it's the default now (utf8mb4)... If someone specified (by error) "utf8" as the collation, is that real utf8 or some other implementation currently?
Redefining `utf8` to mean 4-byte would break the upgrade since existing tables would not be able to join against newly created tables.
This is discussed here: https://mysqlserverteam.com/sushi-beer-an-introduction-of-ut...