support conditional python policy evaluation.

Description: if a python policy implements should_evaluate_policy method, it can choose to have its evaluate a resource or ignore to be part of policy engine evaluation chain.

rpe/engines/python.py

@@ -83,6 +83,13 @@ def evaluate(self, resource):
 
         for policy_name, policy_cls in matched_policies.items():
             try:
+                if hasattr(policy_cls, "should_evaluate_policy"):
+                    should_evaluate_policy_res = policy_cls.should_evaluate_policy(resource)
+                    if not should_evaluate_policy_res:
+                        print(f"Policy: {policy_name}, will not be evaluated for resource {resource} "
+                              f"as should_evaluate_policy returned {should_evaluate_policy_res}")
+                        continue
+
                 if hasattr(policy_cls, "evaluate"):
                     eval_result = policy_cls.evaluate(resource)
                     if not isinstance(eval_result, EvaluationResult):