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

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

-// Copyright (c) 2012, 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.
-
-library pub_tests;
-
-import 'dart:convert';
-
-import 'descriptor.dart' as d;
-import 'test_pub.dart';
-
-main() {
-  initConfig();
-
-  forBothPubGetAndUpgrade((command) {
-    integration('fails gracefully on a dependency from an unknown source', () {
-      d.appDir({
-        "foo": {
-          "bad": "foo"
-        }
-      }).create();
-
-      pubCommand(
-          command,
-          error: 'Package myapp depends on foo from unknown source "bad".');
-    });
-
-    integration(
-        'fails gracefully on transitive dependency from an unknown ' 'source',
-        () {
-      d.dir(
-          'foo',
-          [d.libDir('foo', 'foo 0.0.1'), d.libPubspec('foo', '0.0.1', deps: {
-          "bar": {
-            "bad": "bar"
-          }
-        })]).create();
-
-      d.appDir({
-        "foo": {
-          "path": "../foo"
-        }
-      }).create();
-
-      pubCommand(
-          command,
-          error: 'Package foo depends on bar from unknown source "bad".');
-    });
-
-    integration('ignores unknown source in lockfile', () {
-      d.dir('foo', [d.libDir('foo'), d.libPubspec('foo', '0.0.1')]).create();
-
-      // Depend on "foo" from a valid source.
-      d.dir(appPath, [d.appPubspec({
-          "foo": {
-            "path": "../foo"
-          }
-        })]).create();
-
-      // But lock it to a bad one.
-      d.dir(appPath, [d.file("pubspec.lock", JSON.encode({
-          'packages': {
-            'foo': {
-              'version': '0.0.0',
-              'source': 'bad',
-              'description': {
-                'name': 'foo'
-              }
-            }
-          }
-        }))]).create();
-
-      pubCommand(command);
-
-      // Should upgrade to the new one.
-      d.dir(
-          packagesPath,
-          [d.dir("foo", [d.file("foo.dart", 'main() => "foo";')])]).validate();
-    });
-  });
-}