def unpersistable(self, reason, sxp=None):
        if sxp is None:
            sxp = []
        sxp.append(unpersistable_atom)
        sxp.append(reason)
        return sxp
(internal) Returns an sexp: (unpersistable "reason").  Utility method
dataset/ETHPy150Open nlloyd/SubliminalCollaborator/libs/twisted/spread/jelly.py/_Jellier.unpersistable