def __format_error(self, error_list_tag):
error = {'<STR_LIT>': self.domain(),<EOL>'<STR_LIT>': self.reason(),<EOL>'<STR_LIT:message>': self.message()}<EOL>error.update(self.extra_fields() or {})<EOL>return {'<STR_LIT:error>': {error_list_tag: [error],<EOL>'<STR_LIT:code>': self.status_code(),<EOL>'<STR_LIT:message>': self.message()}}<EOL>
Format this error into a JSON response.

        Args:
          error_list_tag: A string specifying the name of the tag to use for the
            error list.

        Returns:
          A dict containing the reformatted JSON error response.