Remove required on sequence

review348001

stock.py

@@ -2,12 +2,17 @@
 #of this repository contains the full copyright notices and license terms.
 from trytond.model import ModelView, ModelSQL, fields
 from trytond.pyson import Not, Eval, Bool
+from trytond.transaction import Transaction
+from trytond.backend import TableHandler
 
 
 class Location(ModelSQL, ModelView):
     "Stock Location"
     _name = 'stock.location'
-    sequence = fields.Integer('Sequence', required=True, states={
+    sequence = fields.Integer('Sequence',
+        order_field='(%(table)s.sequence IS NULL) %(order)s, '
+        '%(table)s.sequence %(order)s',
+        states={
             'readonly': Not(Bool(Eval('active'))),
             },
         depends=['active'])
@@ -16,4 +21,13 @@ class Location(ModelSQL, ModelView):
         super(Location, self).__init__()
         self._order.insert(0, ('sequence', 'ASC'))
 
+    def init(self, module_name):
+        cursor = Transaction().cursor
+        table = TableHandler(cursor, self, module_name)
+
+        super(Location, self).init(module_name)
+
+        # Migration from 2.4: drop required on sequence
+        table.not_null_action('sequence', action='remove')
+
 Location()