[modules] Improve error messages.

test/mjsunit/modules-fail-4.js

Index: test/mjsunit/modules-fail-4.js
diff --git a/test/mjsunit/modules-fail-4.js b/test/mjsunit/modules-fail-4.js
deleted file mode 100644
index ec9edda9094398851883c637a6e7351949f754ed..0000000000000000000000000000000000000000
--- a/test/mjsunit/modules-fail-4.js
+++ /dev/null
@@ -1,8 +0,0 @@
-// Copyright 2016 the V8 project authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-//
-// MODULE
-
-import {a as b} from "modules-fail-4.js";
-export {c as a} from "modules-fail-4.js";