display the evaluation error when evaluating an expression instead of the NoneType error w/ burnettk

src/spiffworkflow_backend/routes/process_api_blueprint.py

@@ -330,6 +330,8 @@ def process_instance_run(
     if do_engine_steps:
         try:
             processor.do_engine_steps()
+        except ApiError as e:
+            raise e
         except Exception as e:
             ErrorHandlingService().handle_error(processor, e)
             task = processor.bpmn_process_instance.last_task

src/spiffworkflow_backend/services/process_instance_processor.py

@@ -97,6 +97,13 @@ class CustomBpmnScriptEngine(PythonScriptEngine):  # type: ignore
         try:
             return super()._evaluate(expression, context)
         except Exception as exception:
+            if task is None:
+                raise ApiError(
+                    "error_evaluating_expression",
+                    "Error evaluating expression: "
+                    "'%s', exception: %s" % (expression, str(exception)),
+                ) from exception
+            else:
                 raise WorkflowTaskExecException(
                     task,
                     "Error evaluating expression "