Use "package:" imports for pub.

test/hosted/fail_gracefully_on_url_resolve_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
 library pub_tests;
 
-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';
 
 main() {
   initConfig();
 
   forBothPubGetAndUpgrade((command) {
     integration('fails gracefully if the url does not resolve', () {
       d.dir(appPath, [
         d.appPubspec({
           "foo": {
             "hosted": {
               "name": "foo",
               "url": "http://pub.invalid"
             }
           }
         })
       ]).create();
 
       pubCommand(command, error: 'Could not resolve URL "http://pub.invalid".',
           exitCode: exit_codes.UNAVAILABLE);
     });
   });
 }