anchor.diff:    _updateStatus('Downloading docs: $channel $revision');
     return await getBinaryContent(uri);
   }
  +
  +void _printError(e, stack, String message) {
  +  print(message);
  +  print(e);
  +  print(stack);
  +  _updateStatus('$message See console output.');
  +}
  
positive.code:       "$_storageApiBase?prefix=channels/${channel}/${_flavor}/&delimiter=/";
  
    _updateStatus('$channel: getting list');
    var respString = await HttpRequest.getString(url);
  
    Map<String, Object> resp = JSON.decode(respString);
    List<String> versions = (resp["prefixes"] as List<String>);
  
negative.code:           _versionMaps[left], _versionMaps[right], includeComments);
        _updateStatus();
      } catch (e, stack) {
        _printError(e, stack, 'Error comparing versions.');
      }
    } finally {
      _goButton.disabled = false;
  