[FIX]move constraint from the rma order to the line

rma/models/rma_order.py

@@ -2,8 +2,7 @@
 # © 2017 Eficent Business and IT Consulting Services S.L.
 # License LGPL-3.0 or later (https://www.gnu.org/licenses/lgpl.html)
 
-from odoo import api, fields, models, _
-from odoo.exceptions import UserError
+from odoo import api, fields, models
 from datetime import datetime
 
 
@@ -69,16 +68,6 @@ class RmaOrder(models.Model):
                                  required=True, default=lambda self:
                                  self.env.user.company_id)
 
-    @api.constrains("partner_id", "rma_line_ids")
-    def _check_partner_id(self):
-        if self.rma_line_ids and self.partner_id != self.mapped(
-                "rma_line_ids.partner_id"):
-            raise UserError(_(
-                "Group partner and RMA's partner must be the same."))
-        if len(self.mapped("rma_line_ids.partner_id")) > 1:
-            raise UserError(_(
-                "All grouped RMA's should have same partner."))
-
     @api.model
     def create(self, vals):
         if (self.env.context.get('supplier') or

rma/models/rma_order_line.py

@@ -676,3 +676,9 @@ class RmaOrderLine(models.Model):
             result['views'] = [(res and res.id or False, 'form')]
             result['res_id'] = rma_lines.id
         return result
+
+    @api.constrains("partner_id", "rma_id")
+    def _check_partner_id(self):
+        if self.rma_id and self.partner_id != self.rma_id.partner_id:
+            raise ValidationError(_(
+                "Group partner and RMA's partner must be the same."))