[FIX] sale_exception: Make a defensive check before processing table and model rename (#1486)

base_exception/migrations/10.0.2.0.0/pre-migration.py

@@ -8,5 +8,6 @@ from openupgradelib import openupgrade
 @openupgrade.migrate(use_env=True)
 def migrate(env, version):
     cr = env.cr
+    if openupgrade.table_exists('sale_exception'):
         openupgrade.rename_tables(cr, [('sale_exception', 'exception_rule')])
         openupgrade.rename_models(cr, [('sale.exception', 'exception.rule')])