Remove shipment cost method on sale without carrier

Since 34a5debdca00 a domain enforce an empty shipment cost method when no
carrier is selected. So former order must be updated to still be valid.

Closes #12753
(grafted from af20d4f7c1de13bf06fabb1010251884b96b80f7)

--HG--
branch : 7.0

modules/sale_shipment_cost/sale.py

@@ -2,6 +2,8 @@
 # this repository contains the full copyright notices and license terms.
 from decimal import Decimal
 
+from sql import Null
+
 from trytond.i18n import gettext
 from trytond.model import ModelView, Workflow, fields
 from trytond.modules.product import price_digits, round_price
@@ -90,11 +92,20 @@ class Sale(metaclass=PoolMeta):
 
     @classmethod
     def __register__(cls, module):
+        cursor = Transaction().connection.cursor()
+        table = cls.__table__()
+
         super().__register__(module)
         table_h = cls.__table_handler__(module)
         # Migration from 5.8: remove required on shipment_cost_method
         table_h.not_null_action('shipment_cost_method', 'remove')
 
+        # Migration from 6.6: shipment_cost_method domain
+        cursor.execute(*table.update(
+                [table.shipment_cost_method],
+                [Null],
+                where=(table.carrier == Null) & (table.state != 'draft')))
+
     @classmethod
     def default_shipment_cost_method(cls, **pattern):
         Config = Pool().get('sale.configuration')

modules/sale_shipment_cost/setup.py

@@ -41,7 +41,7 @@ else:
     download_url = 'http://downloads.tryton.org/%s.%s/' % (
         major_version, minor_version)
 
-requires = []
+requires = ['python-sql']
 for dep in info.get('depends', []):
     if not re.match(r'(ir|res)(\W|$)', dep):
         requires.append(get_require_version('trytond_%s' % dep))