Enforce the same category of UoM for move with a sale line as origin

The sale line computes the remaining quantity and the quantity to invoice by
converting the move quantity to the sale unit. So they must have the same
category of UoM.

issue6839
review35691002

stock.py

@@ -178,6 +178,18 @@ class Move:
             return 'ignored'
         return ''
 
+    @fields.depends('origin')
+    def on_change_with_product_uom_category(self, name=None):
+        pool = Pool()
+        SaleLine = pool.get('sale.line')
+        category = super(Move, self).on_change_with_product_uom_category(
+            name=name)
+        # Enforce the same unit category as they are used to compute the
+        # remaining quantity to ship and the quantity to invoice.
+        if isinstance(self.origin, SaleLine):
+            category = self.origin.unit.category.id
+        return category
+
     @property
     def origin_name(self):
         pool = Pool()