__init__.py

@@ -1,5 +1,5 @@
 from trytond.pool import Pool
-from . import product, sale, production, invoice
+from . import product, sale, production
 
 __all__ = ['register']
 
@@ -7,7 +7,6 @@ __all__ = ['register']
 def register():
     Pool.register(
         product.Product,
-        invoice.InvoiceLine,
         sale.Sale,
         sale.Line,
         production.Production,

invoice.py

@@ -1,16 +0,0 @@
-from trytond.pool import Pool, PoolMeta
-from trytond.model import ModelView, fields
-from trytond.exceptions import UserError
-from trytond.pyson  import Eval
-
-
-class InvoiceLine(metaclass=PoolMeta):
-    __name__ = 'account.invoice.line'
-
-    @classmethod
-    def __setup__(cls):
-        super(InvoiceLine, cls).__setup__()
-
-        cls.product.states['required'] = (Eval('type') == 'line')
-        cls.unit_price.domain = []
-

tryton.cfg

@@ -6,7 +6,6 @@ depends:
     sale
     sale_supply_production
     production
-    account_invoice
 xml:
     product.xml
     sale.xml

view/sale_form.xml

@@ -3,7 +3,6 @@
      this repository contains the full copyright notices and license terms. -->
 <data>
     <xpath expr="//field[@name='reference']" position="after">
-	<newline/>
 	<label name="pizza_number"/>
 	<field name="pizza_number"/>
 	<button name="add_pizza"/>