Removed TransRealMixin.

Fixed #21688. Refs https://github.com/django/django/pull/1147.

django/test/signals.py

@@ -42,6 +42,9 @@ def update_installed_apps(**kwargs):
         # Rebuild app_template_dirs cache.
         from django.template.loaders import app_directories as mod
         mod.app_template_dirs = mod.calculate_app_template_dirs()
+        # Rebuild translations cache.
+        from django.utils.translation import trans_real
+        trans_real._translations = {}
 
 
 @receiver(setting_changed)
@@ -97,11 +100,14 @@ def clear_serializers_cache(**kwargs):
 
 @receiver(setting_changed)
 def language_changed(**kwargs):
-    if kwargs['setting'] in ('LOCALE_PATHS', 'LANGUAGE_CODE'):
+    if kwargs['setting'] in {'LANGUAGES', 'LANGUAGE_CODE', 'LOCALE_PATHS'}:
         from django.utils.translation import trans_real
         trans_real._default = None
-        if kwargs['setting'] == 'LOCALE_PATHS':
-            trans_real._translations = {}
+        trans_real._active = threading.local()
+    if kwargs['setting'] in {'LANGUAGES', 'LOCALE_PATHS'}:
+        from django.utils.translation import trans_real
+        trans_real._translations = {}
+        trans_real.check_for_language.cache_clear()
 
 
 @receiver(setting_changed)

django/test/utils.py

@@ -2,7 +2,6 @@ from contextlib import contextmanager
 import logging
 import re
 import sys
-from threading import local
 import time
 from unittest import skipUnless
 import warnings
@@ -502,22 +501,6 @@ def patch_logger(logger_name, log_level):
         setattr(logger, log_level, orig)
 
 
-class TransRealMixin(object):
-    """This is the only way to reset the translation machinery. Otherwise
-    the test suite occasionally fails because of global state pollution
-    between tests."""
-    def flush_caches(self):
-        from django.utils.translation import trans_real
-        trans_real._translations = {}
-        trans_real._active = local()
-        trans_real._default = None
-        trans_real.check_for_language.cache_clear()
-
-    def tearDown(self):
-        self.flush_caches()
-        super(TransRealMixin, self).tearDown()
-
-
 # On OSes that don't provide tzset (Windows), we can't set the timezone
 # in which the program runs. As a consequence, we must skip tests that
 # don't enforce a specific timezone (with timezone.override or equivalent),