update prevent_destroy error message

per recommendations by @nathanielks

closes #2473

terraform/context_plan_test.go

@@ -604,7 +604,7 @@ func TestContext2Plan_preventDestroy_bad(t *testing.T) {
 
 	plan, err := ctx.Plan()
 
-	expectedErr := "aws_instance.foo: plan would destroy"
+	expectedErr := "aws_instance.foo: the plan would destroy"
 	if !strings.Contains(fmt.Sprintf("%s", err), expectedErr) {
 		t.Fatalf("expected err would contain %q\nerr: %s\nplan: %s",
 			expectedErr, err, plan)

terraform/eval_check_prevent_destroy.go

@@ -29,4 +29,4 @@ func (n *EvalCheckPreventDestroy) Eval(ctx EvalContext) (interface{}, error) {
 	return nil, nil
 }
 
-const preventDestroyErrStr = `%s: plan would destroy, but resource has prevent_destroy set. To avoid this error, either disable prevent_destroy, or change your config so the plan does not destroy this resource.`
+const preventDestroyErrStr = `%s: the plan would destroy this resource, but it currently has lifecycle.prevent_destroy set to true. To avoid this error and continue with the plan, either disable lifecycle.prevent_destroy or adjust the scope of the plan using the -target flag.`