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

sdk/lib/_internal/pub_generated/test/upgrade/git/upgrade_to_incompatible_pubspec_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 '../../descriptor.dart' as d;
+import '../../test_pub.dart';
+
+main() {
+  initConfig();
+  integration("upgrades Git packages to an incompatible pubspec", () {
+    ensureGit();
+
+    d.git('foo.git', [d.libDir('foo'), d.libPubspec('foo', '1.0.0')]).create();
+
+    d.appDir({
+      "foo": {
+        "git": "../foo.git"
+      }
+    }).create();
+
+    pubGet();
+
+    d.dir(
+        packagesPath,
+        [d.dir('foo', [d.file('foo.dart', 'main() => "foo";')])]).validate();
+
+    d.git('foo.git', [d.libDir('zoo'), d.libPubspec('zoo', '1.0.0')]).commit();
+
+    pubUpgrade(
+        error: contains('"name" field doesn\'t match expected name ' '"foo".'),
+        exitCode: exit_codes.DATA);
+
+    d.dir(
+        packagesPath,
+        [d.dir('foo', [d.file('foo.dart', 'main() => "foo";')])]).validate();
+  });
+}