Fix analyzer hints and warnings in test/.

test/barback/fails_on_all_with_no_buildable_directories_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 'package:pub/src/exit_codes.dart' as exit_codes;
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../descriptor.dart' as d;
-import '../test_pub.dart';
 import 'utils.dart';
 
 main() {
   setUp(() {
     d.appDir().create();
   });
 
   pubBuildAndServeShouldFail("on --all with no default source directories",
       args: ["--all"],
       error: 'There are no source directories present.\n'
         'The default directories are "benchmark", "bin", "example", '
         '"test" and "web".',
       exitCode: exit_codes.DATA);
 }