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

sdk/lib/_internal/pub_generated/lib/src/validator/license.dart

Index: sdk/lib/_internal/pub_generated/lib/src/validator/license.dart
diff --git a/sdk/lib/_internal/pub_generated/lib/src/validator/license.dart b/sdk/lib/_internal/pub_generated/lib/src/validator/license.dart
deleted file mode 100644
index 944b58752b3a0678bf5e975c00b0fd8c53142991..0000000000000000000000000000000000000000
--- a/sdk/lib/_internal/pub_generated/lib/src/validator/license.dart
+++ /dev/null
@@ -1,34 +0,0 @@
-// 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.validator.license;
-
-import 'dart:async';
-
-import 'package:path/path.dart' as path;
-
-import '../entrypoint.dart';
-import '../utils.dart';
-import '../validator.dart';
-
-/// A validator that checks that a LICENSE-like file exists.
-class LicenseValidator extends Validator {
-  LicenseValidator(Entrypoint entrypoint)
-      : super(entrypoint);
-
-  Future validate() {
-    return new Future.sync(() {
-      var licenseLike =
-          new RegExp(r"^([a-zA-Z0-9]+[-_])?(LICENSE|COPYING)(\..*)?$");
-      if (entrypoint.root.listFiles(
-          recursive: false).map(path.basename).any(licenseLike.hasMatch)) {
-        return;
-      }
-
-      errors.add(
-          "You must have a COPYING or LICENSE file in the root directory.\n"
-              "An open-source license helps ensure people can legally use your " "code.");
-    });
-  }
-}