Improve multi-authorizer errors

pkg/auth/authorizer/abac/abac.go

@@ -227,7 +227,7 @@ func (pl policyList) Authorize(a authorizer.Attributes) (authorizer.Decision, st
 			return authorizer.DecisionAllow, "", nil
 		}
 	}
-	return authorizer.DecisionNoOpinion, "No policy matched.", nil
+	return authorizer.DecisionNoOpinion, "no ABAC policy matched", nil
 	// TODO: Benchmark how much time policy matching takes with a medium size
 	// policy file, compared to other steps such as encoding/decoding.
 	// Then, add Caching only if needed.

plugin/pkg/auth/authorizer/rbac/rbac.go

@@ -121,6 +121,8 @@ func (r *RBACAuthorizer) Authorize(requestAttributes authorizer.Attributes) (aut
 	reason := ""
 	if len(ruleCheckingVisitor.errors) > 0 {
 		reason = fmt.Sprintf("RBAC: %v", utilerrors.NewAggregate(ruleCheckingVisitor.errors))
+	} else {
+		reason = "no RBAC policy matched"
 	}
 	return authorizer.DecisionNoOpinion, reason, nil
 }