Hello, I created an extending module which inherits "account.invoice": it adds two fields and shows them in the form view.

Everything works fine until i have to reboot Odoo service, which causes "500 Internal Server Error" after the refresh. I need to remove the module from addons folder, uninstall and reinstall it to make it work again.

My files:

models.py

# -*- coding: utf-8 -*-
from openerp import models, fields, api

class provaextendinvoice(models.Model):
    _inherit = "account.invoice"
    x_field1 = fields.Float(string="Field1")
    x_field2 = fields.Float(string="Field2")

prova_extend_invoice.xml

<openerp>
    <data>
         <record model="ir.ui.view" id="view_invoice_form">
             <field name="name">account.invoice.form.inherit</field>
             <field name="model">account.invoice</field>
             <field name="inherit_id" ref="account.invoice_form"/>
             <field name="arch" type="xml">

                 <field name="amount_untaxed" position="before">
                     <field name="x_field1" readonly="True"/>
                 </field>
                 <field name="amount_untaxed" position="after">
                     <field name="x_field2"readonly="True"/>
                 </field>

             </field>
        </record>
    </data>
</openerp>