trytond-sale_invoice_grouping_shipment_party/message.xml

<?xml version="1.0"?>
<!-- This file is part of Tryton.  The COPYRIGHT file at the top level of
this repository contains the full copyright notices and license terms. -->
<tryton>
    <data grouped="1">
        <record model="ir.message" id="msg_error_party_payer">
            <field name="text">Party "%(name)s" cannot be used as a payer because it has a payer defined</field>
        </record>
    </data>
</tryton>