When a default Boundary Event is added to, say a Service Task, the validation exception is presented as a format string with xml inside a nested exception (i think) instead of a human readable message:
ValidationException: NotImplementedError('Unsupported Catch Event: %r', b'<bpmn:boundaryEvent xmlns:bpmn="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" xmlns:dc="http://www.omg.org/spec/DD/20100524/DC" xmlns:di="http://www.omg.org/spec/DD/20100524/DI" xmlns:spiffworkflow="http://spiffworkflow.org/bpmn/schema/1.0/core" id="Event_1twii2v" attachedToRef="Task_1781606460703"/>\n ').
When a default Boundary Event is added to, say a Service Task, the validation exception is presented as a format string with xml inside a nested exception (i think) instead of a human readable message: