ExtensibleXmlParser error : cvc-complex-type.4: Attribute 'scriptFormat' must appear on element 'drools:onEntry-script' in BPM Suite

Issue

The following error message shows in the kie logs:

ERROR ExtensibleXmlParser:666 - (null: 18, 32): cvc-complex-type.4: Attribute 'scriptFormat' must appear on element 'drools:onEntry-script'.

when executing the following code:

     KieServices ks = KieServices.Factory.get();
     KieContainer kContainer = ks.getKieClasspathContainer();
     kSession = kContainer.newKieSession("my-process");
     kBase = kContainer.getKieBase();
     kSession.startProcess("myprocess_name");