Only support the new source_span spans in barback.

pkg/barback/lib/src/graph/package_graph.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 barback.graph.package_graph;
 
 import 'dart:async';
 import 'dart:collection';
 
 import '../asset/asset_id.dart';
@@ skipping 190 matching lines @@
     }
 
     if (_logController.hasListener) {
       _logController.add(entry);
     } else if (entry.level != LogLevel.FINE) {
       // No listeners, so just print entry.
       var buffer = new StringBuffer();
       buffer.write("[${entry.level} ${entry.transform}] ");
 
       if (entry.span != null) {
-        buffer.write(entry.span.getLocationMessage(entry.message));
+        buffer.write(entry.span.message(entry.message));
       } else {
         buffer.write(entry.message);
       }
 
       print(buffer);
     }
   }
 
   /// If [this] is done processing, schedule a [BuildResult] to be emitted on
   /// [results].
@@ skipping 31 matching lines @@
         completer.completeError(error, stackTrace);
       });
     }, onError: (error, stackTrace) {
       _lastUnexpectedError = error;
       _lastUnexpectedErrorTrace = stackTrace;
       _resultsController.addError(error, stackTrace);
     });
     return completer.future;
   }
 }