Use "package:" imports for pub.

test/hosted/fail_gracefully_on_missing_package_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';
 import '../test_pub.dart';
 
 main() {
   initConfig();
 
   forBothPubGetAndUpgrade((command) {
     integration('fails gracefully if the package does not exist', () {
       serveNoPackages();
 
       d.appDir({"foo": "1.2.3"}).create();
 
       pubCommand(command, error: new RegExp(r"""
 Could not find package foo at http://localhost:\d+\.
 Depended on by:
 - myapp""", multiLine: true),
           exitCode: exit_codes.UNAVAILABLE);
     });
   });
 }