Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/run/nonexistent_dependency_test.dart

Index: sdk/lib/_internal/pub_generated/test/run/nonexistent_dependency_test.dart
diff --git a/sdk/lib/_internal/pub_generated/test/run/nonexistent_dependency_test.dart b/sdk/lib/_internal/pub_generated/test/run/nonexistent_dependency_test.dart
deleted file mode 100644
index f57ce49f9bbecc02015d21f7152d7817d14c0541..0000000000000000000000000000000000000000
--- a/sdk/lib/_internal/pub_generated/test/run/nonexistent_dependency_test.dart
+++ /dev/null
@@ -1,19 +0,0 @@
-// 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 '../descriptor.dart' as d;
-import '../test_pub.dart';
-
-main() {
-  initConfig();
-  integration('Errors if the script is in an unknown package.', () {
-    d.dir(appPath, [d.appPubspec()]).create();
-
-    var pub = pubRun(args: ["foo:script"]);
-    pub.stderr.expect(
-        'Could not find package "foo". Did you forget to add a ' 'dependency?');
-    pub.shouldExit(exit_codes.DATA);
-  });
-}