Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/lish/package_validation_has_an_error_test.dart

-// Copyright (c) 2013, 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:scheduled_test/scheduled_server.dart';
-import 'package:scheduled_test/scheduled_stream.dart';
-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';
-
-main() {
-  initConfig();
-  setUp(d.validPackage.create);
-
-  integration('package validation has an error', () {
-    var pkg = packageMap("test_pkg", "1.0.0");
-    pkg.remove("homepage");
-    d.dir(appPath, [d.pubspec(pkg)]).create();
-
-    var server = new ScheduledServer();
-    var pub = startPublish(server);
-
-    pub.shouldExit(exit_codes.SUCCESS);
-    pub.stderr.expect(
-        consumeThrough(
-            "Sorry, your package is missing a " "requirement and can't be published yet."));
-  });
-}