pkg: analysis aided cleanup

pkg/scheduled_test/test/scheduled_test/abort_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.
 
 import 'dart:async';
-import 'dart:io';
 
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../metatest.dart';
 import '../utils.dart';
 
 void main() {
   setUpTimeout();
 
   expectTestsPass("aborting the schedule before it's started running should "
@@ skipping 68 matching lines @@
   expectTestsFail("aborting the schedule after an out-of-band error should "
       "still surface the error", () {
     test('test', () {
       schedule(() {
         currentSchedule.signalError('error');
         currentSchedule.abort();
       });
     });
   });
 }