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

sdk/lib/_internal/pub_generated/test/get/path/nonexistent_dir_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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 d.file.
 
 import 'package:path/path.dart' as path;
 
 import '../../../lib/src/exit_codes.dart' as exit_codes;
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
 main() {
   initConfig();
   integration('path dependency to non-existent directory', () {
     var badPath = path.join(sandboxDir, "bad_path");
 
-    d.dir(appPath, [
-      d.appPubspec({
-        "foo": {"path": badPath}
-      })
-    ]).create();
+    d.dir(appPath, [d.appPubspec({
+        "foo": {
+          "path": badPath
+        }
+      })]).create();
 
     pubGet(error: """
         Could not find package foo at "$badPath".
         Depended on by:
-        - myapp 0.0.0""",
-        exitCode: exit_codes.UNAVAILABLE);
+        - myapp 0.0.0""", exitCode: exit_codes.UNAVAILABLE);
   });
-}
+}