Revert "Use native async/await support in pub."

sdk/lib/_internal/pub_generated/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();
+    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);
+    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);
   });
-}
+}