Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/run/does_not_run_on_transformer_error_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 '../descriptor.dart' as d;
-import '../test_pub.dart';
-
-const SCRIPT = """
-main() {
-  print("should not get here!");
-}
-""";
-
-const TRANSFORMER = """
-import 'dart:async';
-
-import 'package:barback/barback.dart';
-
-class FailingTransformer extends Transformer {
-  FailingTransformer.asPlugin();
-
-  String get allowedExtensions => '.dart';
-
-  void apply(Transform transform) {
-    // Don't run on the transformer itself.
-    if (transform.primaryInput.id.path.startsWith("lib")) return;
-    transform.logger.error('\${transform.primaryInput.id}.');
-  }
-}
-""";
-
-main() {
-  initConfig();
-  withBarbackVersions("any", () {
-    integration('does not run if a transformer has an error', () {
-      d.dir(appPath, [d.pubspec({
-          "name": "myapp",
-          "transformers": ["myapp/src/transformer"]
-        }),
-            d.dir("lib", [d.dir("src", [d.file("transformer.dart", TRANSFORMER)])]),
-            d.dir("bin", [d.file("script.dart", SCRIPT)])]).create();
-
-      createLockFile('myapp', pkg: ['barback']);
-
-      var pub = pubRun(args: ["script"]);
-
-      pub.stderr.expect("[Error from Failing]:");
-      pub.stderr.expect("myapp|bin/script.dart.");
-
-      // Note: no output from the script.
-      pub.shouldExit();
-    });
-  });
-}