Run pub tests against older versions of barback.

third_party/pkg/barback-0.13.0/lib/src/lazy_transformer.dart

 // Copyright (c) 2014, 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 barback.transformer.lazy_transformer;
+library barback.lazy_transformer;
 
 import 'declaring_transformer.dart';
 
 /// An interface for [Transformer]s that indicates that the transformer's
 /// outputs shouldn't be generated until requested.
 ///
 /// The [declareOutputs] method is used to figure out which assets should be
 /// treated as "lazy." Lazy assets will only be forced to be generated if
 /// they're requested by the user or if they're used by a non-declaring
 /// transformer.
 abstract class LazyTransformer extends DeclaringTransformer {}