Use shelf handlers in ScheduledServer.

sdk/lib/_internal/pub/test/lish/force_publishes_if_there_are_warnings_test.dart

Index: sdk/lib/_internal/pub/test/lish/force_publishes_if_there_are_warnings_test.dart
diff --git a/sdk/lib/_internal/pub/test/lish/force_publishes_if_there_are_warnings_test.dart b/sdk/lib/_internal/pub/test/lish/force_publishes_if_there_are_warnings_test.dart
index 85ce297148929a7716006b2178c42cb7deaa6d01..c6e19ca0e2da4423f0ef7c9151abf52de86bc71d 100644
--- a/sdk/lib/_internal/pub/test/lish/force_publishes_if_there_are_warnings_test.dart
+++ b/sdk/lib/_internal/pub/test/lish/force_publishes_if_there_are_warnings_test.dart
@@ -7,6 +7,7 @@ import 'dart:convert';
 import 'package:scheduled_test/scheduled_server.dart';
 import 'package:scheduled_test/scheduled_stream.dart';
 import 'package:scheduled_test/scheduled_test.dart';
+import 'package:shelf/shelf.dart' as shelf;
 
 import '../../lib/src/exit_codes.dart' as exit_codes;
 import '../descriptor.dart' as d;
@@ -30,10 +31,9 @@ main() {
     handleUpload(server);
 
     server.handle('GET', '/create', (request) {
-      request.response.write(JSON.encode({
+      return new shelf.Response.ok(JSON.encode({
         'success': {'message': 'Package test_pkg 1.0.0 uploaded!'}
       }));
-      request.response.close();
     });
 
     pub.shouldExit(exit_codes.SUCCESS);