[FIX] base_exception: Migration scripts

Current method doesn't work, as this module is not being migrated, but
fresh-installed by dependencies of old `sale_exception`, so we should use
the pre_init_hook and detect if we should run the migration code according the
existence of the table.

base_exception/__init__.py

@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-# © 2011 Raphaël Valyi, Renato Lima, Guewen Baconnier, Sodexis
 # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
 
 from . import wizard, models
+from .hooks import pre_init_hook

base_exception/__manifest__.py

@@ -18,4 +18,5 @@
      'views/base_exception_view.xml',
  ],
  'installable': True,
+ 'pre_init_hook': 'pre_init_hook',
  }

base_exception/hooks.py

@@ -0,0 +1,17 @@
+# -*- coding: utf-8 -*-
+# Copyright 2017 Akretion, Mourad EL HADJ MIMOUNE
+# Copyright 2018 Tecnativa - Pedro M. Baeza
+# License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl.html).
+
+
+def pre_init_hook(cr):
+    """If coming from v9 where only `sale_exception` is installed, when
+    auto-installing this one by dependencies, we should take care of
+    renaming previous table before the new model is loaded.
+    """
+    cr.execute("SELECT 1 FROM pg_class WHERE relname = 'sale_exception'")
+    if not cr.fetchone():
+        return  # fresh install, so exiting
+    from openupgradelib import openupgrade
+    openupgrade.rename_tables(cr, [('sale_exception', 'exception_rule')])
+    openupgrade.rename_models(cr, [('sale.exception', 'exception.rule')])

base_exception/migrations/10.0.1.0.0/pre-migration.py

@@ -1,12 +0,0 @@
-# -*- coding: utf-8 -*-
-# © 2017 Akretion, Mourad EL HADJ MIMOUNE
-# License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl.html).
-
-from openupgradelib import openupgrade
-
-
-@openupgrade.migrate(use_env=True)
-def migrate(env, version):
-    cr = env.cr
-    openupgrade.rename_tables(cr, [('sale_exception', 'exception_rule')])
-    openupgrade.rename_models(cr, [('sale.exception', 'exception.rule')])