anchor.diff:      _fileService.call(request).then((response) {
         _writeCompleted();
         if (_isErrorResponse(response)) {
  -        _handleErrorResponse(response, "writeList failed");
  +        _handleErrorResponse(response, "writeList failed for file '$_name'");
         }
       });
     }
  
positive.code:     };
      var result = create(name);
      if (result is OSError) {
        throw new FileIOException("Cannot create file", result);
      }
      return true;
    }
  
negative.code:     _fileService.call(request).then((response) {
        _writeCompleted();
        if (_isErrorResponse(response)) {
          _handleErrorResponse(response, "writeString failed for file '$_name'");
        }
      });
    }
  