Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/global/binstubs/does_not_warn_if_no_executables_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 'dart:io';
-
-import 'package:path/path.dart' as p;
-import 'package:scheduled_test/scheduled_test.dart';
-
-import '../../descriptor.dart' as d;
-import '../../test_pub.dart';
-
-main() {
-  initConfig();
-  integration("does not warn if the package has no executables", () {
-    servePackages((builder) {
-      builder.serve(
-          "foo",
-          "1.0.0",
-          contents: [
-              d.dir("bin", [d.file("script.dart", "main(args) => print('ok \$args');")])]);
-    });
-
-    schedulePub(
-        args: ["global", "activate", "foo"],
-        output: isNot(contains("is not on your path")));
-  });
-}