Checks if a task is revoked, returns a 2-tuple indicating:

        1. Is task revoked?
        2. Should task be restored?

def _check_revoked(self, revoke_id, timestamp=None, peek=True):
        """
        Checks if a task is revoked, returns a 2-tuple indicating:

        1. Is task revoked?
        2. Should task be restored?
        """
        res = self.get(revoke_id, peek=True)
        if res is None:
            return False, False

        revoke_until, revoke_once = res
        if revoke_until is not None and timestamp is None:
            timestamp = self._get_timestamp()

        if revoke_once:
            # This task *was* revoked for one run, but now it should be
            # restored to normal execution (unless we are just peeking).
            return True, not peek
        elif revoke_until is not None and revoke_until <= timestamp:
            # Task is no longer revoked and can be restored.
            return False, not peek
        else:
            # Task is still revoked. Do not restore.
            return True, False