pkg/scheduled_test: fix analyzer hints

lib/scheduled_server.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 scheduled_test.scheduled_server;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:io';
 
 import 'package:http_multi_server/http_multi_server.dart';
 import 'package:shelf/shelf.dart' as shelf;
 import 'package:shelf/shelf_io.dart' as shelf_io;
 
 import 'scheduled_test.dart';
 import 'src/scheduled_server/handler.dart';
-import 'src/utils.dart';
 
 /// A class representing an HTTP server that's scheduled to run in the course of
 /// the test. This class allows the server's request handling to be scheduled
 /// synchronously.
 ///
 /// The server expects requests to be received in the order [handle] is called,
 /// and expects that no additional requests will be received.
 class ScheduledServer {
   /// The description of the server.
   final String description;
@@ skipping 69 matching lines @@
       return _handlers.removeFirst().fn(request);
     }).catchError((error, stackTrace) {
       registerException(error, stackTrace);
 
       return new shelf.Response.internalServerError(
           body: error.toString(),
           headers: {'content-type': 'text/plain'});
     });
   }
 }