Restore English language on tear down

The translations tests change the default language on setup and commit the
change. So we must restore the initial state of the database at the end of the
test case.

issue9702
review312521002

trytond/ir/configuration.py

@@ -31,3 +31,19 @@ class Configuration(ModelSingleton, ModelSQL):
     def check(self):
         "Check configuration coherence on pool initialisation"
         pass
+
+    @classmethod
+    def create(cls, vlist):
+        records = super().create(vlist)
+        cls._get_language_cache.clear()
+        return records
+
+    @classmethod
+    def write(cls, *args):
+        super().write(*args)
+        cls._get_language_cache.clear()
+
+    @classmethod
+    def delete(cls, records):
+        super().delete(records)
+        cls._get_language_cache.clear()

trytond/tests/test_modelsql.py

@@ -555,6 +555,32 @@ class ModelSQLTranslationTestCase(unittest.TestCase):
 
         Transaction().commit()
 
+    @classmethod
+    def tearDownClass(cls):
+        super().tearDownClass()
+        cls.restore_language()
+
+    @classmethod
+    @with_transaction()
+    def restore_language(cls):
+        pool = Pool()
+        Language = pool.get('ir.lang')
+        Configuration = pool.get('ir.configuration')
+
+        english, = Language.search([('code', '=', 'en')])
+        english.translatable = True
+        english.save()
+
+        config = Configuration(1)
+        config.language = 'en'
+        config.save()
+
+        Language.write(Language.search([('code', '!=', 'en')]), {
+                'translatable': False,
+                })
+
+        Transaction().commit()
+
     @with_transaction()
     def test_create_default_language(self):
         "Test create default language"