Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/global/run/missing_executable_arg_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 '../../../lib/src/exit_codes.dart' as exit_codes;
-import '../../test_pub.dart';
-
-main() {
-  initConfig();
-  integration('fails if no executable was given', () {
-    schedulePub(args: ["global", "run"], error: """
-            Must specify an executable to run.
-
-            Usage: pub global run <package>:<executable> [args...]
-            -h, --help    Print this usage information.
-                --mode    Mode to run transformers in.
-                          (defaults to "release")
-
-            Run "pub help" to see global options.
-            """, exitCode: exit_codes.USAGE);
-  });
-}