MySQL error 1452 in kea-admin tests

The last MySQAL test mysql_unused_subnet_id_test raised an error which does not make it to fail:

Processing /tmp/k1196/src/share/database/scripts/mysql/upgrade_9.1_to_9.2.sh file...
ERROR 1452 (23000) at line 8: Cannot add or update a child row: a foreign key constraint fails (`keatest`.`#sql-22f3_4b5d`, CONSTRAINT `fk_dhcp4_options_subnet` FOREIGN KEY (`dhcp4_subnet_id`) REFERENCES `dhcp4_subnet` (`subnet_id`) ON DELETE CASCADE ON UPDATE CASCADE)
Processing /tmp/k1196/src/share/database/scripts/mysql/upgrade_9.2_to_9.3.sh file...
This script upgrades 9.2 to 9.3. Reported version is 9.1. Skipping upgrade.
Database version reported after upgrade: 9.1

Wiping whole database keatest
PASSED mysql.unused_subnet_id_test

I think the second (subnet) new constraint fails, something as having a subnet option when the subnet itself does not exist.