[FIX] add missing exceptions import

Author: ManfredNelvin-Dev

stock_account_operating_unit/tests/test_stock_account_operating_unit.py

@@ -2,6 +2,7 @@
 # - Jordi Ballester Alomar
 # © 2019 Serpent Consulting Services Pvt. Ltd. - Sudhir Arya
 # License LGPL-3.0 or later (https://www.gnu.org/licenses/lgpl.html).
+from odoo import exceptions
 from odoo.tests import Form
 
 from odoo.addons.stock.tests.common import TestStockCommon