Revert "Revert "Use native async/await support in pub.""

sdk/lib/_internal/pub_generated/test/pub_test.dart

-// Copyright (c) 2012, 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.
-
-library pub_tests;
-
-import 'package:scheduled_test/scheduled_test.dart';
-
-import '../lib/src/exit_codes.dart' as exit_codes;
-import 'test_pub.dart';
-
-main() {
-  initConfig();
-
-  integration('running pub with no command displays usage', () {
-    schedulePub(args: [], output: """
-        Pub is a package manager for Dart.
-
-        Usage: pub <command> [arguments]
-
-        Global options:
-        -h, --help            Print this usage information.
-            --version         Print pub version.
-            --[no-]trace      Print debugging information when an error occurs.
-            --verbosity       Control output verbosity.
-
-                  [all]       Show all output including internal tracing messages.
-                  [io]        Also show IO operations.
-                  [normal]    Show errors, warnings, and user messages.
-                  [solver]    Show steps during version resolution.
-
-        -v, --verbose         Shortcut for "--verbosity=all".
-
-        Available commands:
-          build       Apply transformers to build a package.
-          cache       Work with the system cache.
-          deps        Print package dependencies.
-          downgrade   Downgrade the current package's dependencies to oldest versions.
-          get         Get the current package's dependencies.
-          global      Work with global packages.
-          help        Display help information for pub.
-          publish     Publish the current package to pub.dartlang.org.
-          run         Run an executable from a package.
-          serve       Run a local web development server.
-          upgrade     Upgrade the current package's dependencies to latest versions.
-          uploader    Manage uploaders for a package on pub.dartlang.org.
-          version     Print pub version.
-
-        Run "pub help <command>" for more information about a command.
-        See http://dartlang.org/tools/pub for detailed documentation.
-        """);
-  });
-
-  integration('running pub with just --version displays version', () {
-    schedulePub(args: ['--version'], output: 'Pub 0.1.2+3');
-  });
-}