Use "package:" imports for pub.

test/dart2js/does_not_support_invalid_option_test.dart

Index: test/dart2js/does_not_support_invalid_option_test.dart
diff --git a/test/dart2js/does_not_support_invalid_option_test.dart b/test/dart2js/does_not_support_invalid_option_test.dart
index 1d299198287c0362b121e8e29ec6cf5d0ad10c99..93c0cdc3cd37f70b20d01c96b1598d331602e8a7 100644
--- a/test/dart2js/does_not_support_invalid_option_test.dart
+++ b/test/dart2js/does_not_support_invalid_option_test.dart
@@ -2,7 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import '../../lib/src/exit_codes.dart' as exit_codes;
+import 'package:pub/src/exit_codes.dart' as exit_codes;
+
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
 import '../serve/utils.dart';