Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/barback/fails_on_overlapping_directories_test.dart

-// Copyright (c) 2014, 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.
-
-import 'package:path/path.dart' as path;
-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';
-import 'utils.dart';
-
-main() {
-  initConfig();
-
-  setUp(() {
-    d.dir(
-        appPath,
-        [
-            d.appPubspec(),
-            d.dir(
-                "web",
-                [
-                    d.dir(
-                        "sub1",
-                        [
-                            d.file("file.txt", "contents"),
-                            d.dir("sub2", [d.file("file.txt", "contents")]),
-                            d.dir("sub3", [d.file("file.txt", "contents")])])])]).create();
-  });
-
-  var webSub1 = path.join("web", "sub1");
-  var webSub1Sub2 = path.join("web", "sub1", "sub2");
-  var webSub1Sub3 = path.join("web", "sub1", "sub3");
-
-  pubBuildAndServeShouldFail(
-      "if a superdirectory follows a subdirectory",
-      args: [webSub1Sub2, webSub1],
-      error: 'Directories "$webSub1Sub2" and "$webSub1" cannot overlap.',
-      exitCode: exit_codes.USAGE);
-
-  pubBuildAndServeShouldFail(
-      "if a subdirectory follows a superdirectory",
-      args: [webSub1, webSub1Sub2],
-      error: 'Directories "$webSub1" and "$webSub1Sub2" cannot overlap.',
-      exitCode: exit_codes.USAGE);
-
-  pubBuildAndServeShouldFail(
-      "if multiple directories overlap",
-      args: [webSub1, webSub1Sub2, webSub1Sub3],
-      error: 'Directories "$webSub1", "$webSub1Sub2" and "$webSub1Sub3" '
-          'cannot overlap.',
-      exitCode: exit_codes.USAGE);
-}