def METHOD_NAME(self):
    fee_rate = self.feerate_e.get_amount()
    if fee_rate is None:
        self.tx = None
        self.error = _('No fee rate')
    elif fee_rate <= self.old_fee_rate:
        self.tx = None
        self.error = _("The new fee rate needs to be higher than the old fee rate.")
    else:
        try:
            self.tx = self.make_tx(fee_rate)
        except CannotRBFTx as e:
            self.tx = None
            self.error = str(e)