Poner límite de la cantidad del lineas de ventas

__init__.py

@@ -0,0 +1,3 @@
+# -*- coding: utf-8 -*-
+
+from . import models

__openerp__.py

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+# -*- coding: utf-8 -*-
+
+{
+    'name': "Limitar Producto en Linea de Ventas",
+    'author': "Adrielso Kunert",
+    'category': 'Sales Management',
+    'version': '8.0.0.1',
+    'depends': ['sale'],
+    'installable':True,
+    'auto_install':False
+}

models/__init__.py

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+# -*- coding: utf-8 -*-
+
+from . import sale_order

models/sale_order.py

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+# -*- coding: utf-8 -*-
+from openerp import models,fields,api,_
+from openerp.exceptions import Warning
+
+class sale_order(models.Model):
+    _inherit = 'sale.order'
+
+    @api.multi
+    def action_button_confirm(self):
+        message1 = ""
+        limite = 11
+        if len(self.order_line) > limite:
+            message1 += "La cantidad de Linea supera la cantidad permitida para la venta"
+            message1 += "\n Cantidad Actual "+str(len(self.order_line))+" lineas"
+            message1 += "\n Cantidad Permitida "+str(limite)+" lineas"
+
+        if message1:
+            raise Warning(_(message1.rstrip()))
+
+        return super(sale_order,self).action_button_confirm()