Start pulling pub from its own repo.

sdk/lib/_internal/pub/test/list_package_dirs/pubspec_error_test.dart

-// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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 d.file.
-
-import 'package:path/path.dart' as path;
-import 'package:scheduled_test/scheduled_test.dart';
-
-import '../../lib/src/exit_codes.dart' as exit_codes;
-import '../../lib/src/io.dart';
-import '../descriptor.dart' as d;
-import '../test_pub.dart';
-
-main() {
-  initConfig();
-  integration("reports the pubspec path when there is an error in it", () {
-    d.dir(appPath, [
-      d.file("pubspec.yaml", "some bad yaml")
-    ]).create();
-
-    schedulePub(args: ["list-package-dirs", "--format=json"],
-        outputJson: {
-          "error": contains('Error on line 1'),
-          "path": canonicalize(path.join(sandboxDir, appPath, "pubspec.yaml"))
-        },
-        exitCode: exit_codes.DATA);
-  });
-}