This code

        SystemEventListener listener =  SystemEventListenerFactory.getSystemEventListener();

Fails with:

Caused by: java.lang.ClassNotFoundException: org.drools.core.impl.SystemEventListenerServiceImpl

Because ServiceRegistryImpl
https://github.com/droolsjbpm/droolsjbpm-knowledge/blob/master/kie-internal/src/main/java/org/kie/internal/utils/ServiceRegistryImpl.java#L189
references class SystemEventListenerServiceImpl which does not exist anymore in drools-core.

The interface SystemEventListenerService still exists in kie-internal but there is no implementation whatsoever in drools.

First impression is that both SystemEventListenerService + SystemEventListenerServiceImpl are "dead" code and should probably be removed.