Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/upgrade/report/leading_character_shows_change_test.dart

-// Copyright (c) 2013, 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 '../../descriptor.dart' as d;
-import '../../test_pub.dart';
-
-main() {
-  initConfig();
-  integration("the character before each package describes the change", () {
-    servePackages((builder) {
-      builder.serve("added", "1.0.0");
-      builder.serve("downgraded", "1.0.0");
-      builder.serve("downgraded", "2.0.0");
-      builder.serve("overridden", "1.0.0");
-      builder.serve("removed", "1.0.0");
-      builder.serve("source_changed", "1.0.0");
-      builder.serve("upgraded", "1.0.0");
-      builder.serve("upgraded", "2.0.0");
-      builder.serve("unchanged", "1.0.0");
-    });
-
-    d.dir(
-        "description_changed_1",
-        [
-            d.libDir("description_changed"),
-            d.libPubspec("description_changed", "1.0.0")]).create();
-
-    d.dir(
-        "description_changed_2",
-        [
-            d.libDir("description_changed"),
-            d.libPubspec("description_changed", "1.0.0")]).create();
-
-    d.dir(
-        "source_changed",
-        [d.libDir("source_changed"), d.libPubspec("source_changed", "1.0.0")]).create();
-
-    // Create the first lockfile.
-    d.dir(appPath, [d.pubspec({
-        "name": "myapp",
-        "dependencies": {
-          "description_changed": {
-            "path": "../description_changed_1"
-          },
-          "downgraded": "2.0.0",
-          "removed": "any",
-          "source_changed": "any",
-          "unchanged": "any",
-          "upgraded": "1.0.0"
-        },
-        "dependency_overrides": {
-          "overridden": "any"
-        }
-      })]).create();
-
-    pubGet();
-
-    // Change the pubspec.
-    d.dir(appPath, [d.pubspec({
-        "name": "myapp",
-        "dependencies": {
-          "added": "any",
-          "description_changed": {
-            "path": "../description_changed_2"
-          },
-          "downgraded": "1.0.0",
-          "source_changed": {
-            "path": "../source_changed"
-          },
-          "unchanged": "any",
-          "upgraded": "2.0.0"
-        },
-        "dependency_overrides": {
-          "overridden": "any"
-        }
-      })]).create();
-
-    // Upgrade everything.
-    pubUpgrade(output: new RegExp(r"""
-Resolving dependencies\.\.\..*
-\+ added .*
-\* description_changed .*
-< downgraded .*
-! overridden .*
-\* source_changed .*
-  unchanged .*
-> upgraded .*
-These packages are no longer being depended on:
-- removed .*
-""", multiLine: true));
-  });
-}