Require a carrier to quote sale with shipment cost method

Closes #11985

modules/sale_shipment_cost/CHANGELOG

@@ -1,3 +1,5 @@
+* Require carrier to quote sale with shipment cost method
+
 Version 6.6.0 - 2022-10-31
 --------------------------
 * Bug fixes (see mercurial logs for details)

modules/sale_shipment_cost/message.xml

@@ -6,6 +6,9 @@ this repository contains the full copyright notices and license terms. -->
         <record model="ir.message" id="msg_sale_invalid_carrier">
             <field name="text">To confirm sale "%(sale)s" you must change the carrier "%(carrier)s".</field>
         </record>
+        <record model="ir.message" id="msg_sale_carrier_required_for_quotation">
+            <field name="text">To get a quote for sale "%(sale)s" you must enter a carrier.</field>
+        </record>
         <record model="ir.message" id="msg_shipment_cost_invoice_missing_account_revenue">
             <field name="text">To invoice shipment cost of "%(shipment)s", you must define an account revenue for product "%(product)s".</field>
         </record>

modules/sale_shipment_cost/sale.py

@@ -6,7 +6,8 @@ from trytond import backend
 from trytond.i18n import gettext
 from trytond.model import ModelView, Workflow, fields
 from trytond.modules.product import price_digits, round_price
-from trytond.modules.sale.exceptions import SaleConfirmError
+from trytond.modules.sale.exceptions import (
+    SaleConfirmError, SaleQuotationError)
 from trytond.pool import Pool, PoolMeta
 from trytond.pyson import Eval, If
 from trytond.transaction import Transaction
@@ -198,6 +199,19 @@ class Sale(metaclass=PoolMeta):
         elif not self.available_carriers:
             self.carrier = None
 
+    def check_for_quotation(self):
+        super().check_for_quotation()
+        if self.shipment_cost_method and self.available_carriers:
+            for line in self.lines:
+                if (line.product
+                        and line.product.type != 'service'
+                        and line.quantity >= 0
+                        and not self.carrier):
+                    raise SaleQuotationError(
+                        gettext('sale'
+                            '.msg_sale_carrier_required_for_quotation',
+                            sale=self.rec_name))
+
     @classmethod
     @ModelView.button
     @Workflow.transition('quotation')