Unapprove the merge request.

        Args:
            **kwargs: Extra options to send to the server (e.g. sudo)

        Raises:
            GitlabAuthenticationError: If authentication is not correct
            GitlabMRApprovalError: If the unapproval failed

def unapprove(self, **kwargs):
        """Unapprove the merge request.

        Args:
            **kwargs: Extra options to send to the server (e.g. sudo)

        Raises:
            GitlabAuthenticationError: If authentication is not correct
            GitlabMRApprovalError: If the unapproval failed
        """
        path = '%s/%s/unapprove' % (self.manager.path, self.get_id())
        data = {}

        server_data = self.manager.gitlab.http_post(path, post_data=data,
                                                    **kwargs)
        self._update_attrs(server_data)