Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/list_package_dirs/lockfile_error_test.dart

Index: sdk/lib/_internal/pub_generated/test/list_package_dirs/lockfile_error_test.dart
diff --git a/sdk/lib/_internal/pub_generated/test/list_package_dirs/lockfile_error_test.dart b/sdk/lib/_internal/pub_generated/test/list_package_dirs/lockfile_error_test.dart
deleted file mode 100644
index d9b872a7c5ffe83f6e1fa33e2bacd08935090f94..0000000000000000000000000000000000000000
--- a/sdk/lib/_internal/pub_generated/test/list_package_dirs/lockfile_error_test.dart
+++ /dev/null
@@ -1,25 +0,0 @@
-// 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 lockfile path when there is an error in it", () {
-    d.dir(
-        appPath,
-        [d.appPubspec(), d.file("pubspec.lock", "some bad yaml")]).create();
-
-    schedulePub(args: ["list-package-dirs", "--format=json"], outputJson: {
-      "error": contains('The lockfile must be a YAML mapping.'),
-      "path": canonicalize(path.join(sandboxDir, appPath, "pubspec.lock"))
-    }, exitCode: exit_codes.DATA);
-  });
-}