[9.0] rma_purchase: add purchase_policy

cherry-pick 2100329188e45bf465d43b47c7e45cdb5041bc11

rma_purchase/models/rma_operation.py

@@ -0,0 +1,25 @@
+# -*- coding: utf-8 -*-
+# Copyright 2018 Eficent Business and IT Consulting Services S.L.
+# License LGPL-3.0 or later (https://www.gnu.org/licenses/lgpl.html)
+
+from openerp import api, fields, models, _
+from openerp.exceptions import ValidationError
+
+
+class RmaOperation(models.Model):
+    _inherit = 'rma.operation'
+
+    purchase_policy = fields.Selection(
+        selection=[('no', 'Not required'),
+                   ('ordered', 'Based on Ordered Quantities'),
+                   ('delivered', 'Based on Delivered Quantities')],
+        string="Purchase Policy", default='no',
+    )
+
+    @api.multi
+    @api.constrains('purchase_policy')
+    def _check_purchase_policy(self):
+        if self.filtered(
+                lambda r: r.purchase_policy != 'no' and r.type != 'supplier'):
+            raise ValidationError(_(
+                'Purchase Policy can only apply to supplier operations'))