Use "package:" imports for pub.

test/get/git/require_pubspec_name_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 'package:pub/src/exit_codes.dart' as exit_codes;
 import 'package:scheduled_test/scheduled_test.dart';
 
-import '../../../lib/src/exit_codes.dart' as exit_codes;
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
 main() {
   initConfig();
   integration('requires the dependency to have a pubspec with a name '
       'field', () {
     ensureGit();
 
     d.git('foo.git', [
       d.libDir('foo'),
       d.pubspec({})
     ]).create();
 
     d.appDir({"foo": {"git": "../foo.git"}}).create();
 
     pubGet(error: contains('Missing the required "name" field.'),
         exitCode: exit_codes.DATA);
   });
 }