anchor.diff:      request[1] = _name;
       _fileService.call(request).then((response) {
         if (_isErrorResponse(response)) {
  -        _handleErrorResponse(response, "Cannot delete file");
  +        _handleErrorResponse(response, "Cannot delete file '$_name'");
         } else {
           callback();
         }
  
positive.code:     request[1] = _id;
      _fileService.call(request).then((response) {
        if (_isErrorResponse(response)) {
          _handleErrorResponse(response, "readByte failed");
        } else {
          callback(response);
        }
  
negative.code:     request[1] = _id;
      _fileService.call(request).then((response) {
        if (_isErrorResponse(response)) {
          _handleErrorResponse(response, "length failed for file '$_name'");
        } else {
          callback(response);
        }
  