[1.6.x] Fixed #21307 -- Moved TransRealMixin to django.test.utils.

51d2e1fb23 from master.

django/contrib/humanize/tests.py

@@ -11,7 +11,7 @@ from django.conf import settings
 from django.contrib.humanize.templatetags import humanize
 from django.template import Template, Context, defaultfilters
 from django.test import TestCase
-from django.test.utils import override_settings
+from django.test.utils import override_settings, TransRealMixin
 from django.utils.html import escape
 from django.utils.timezone import utc
 from django.utils import translation
@@ -19,8 +19,6 @@ from django.utils.translation import ugettext as _
 from django.utils import tzinfo
 from django.utils.unittest import skipIf
 
-from i18n import TransRealMixin
-
 
 # Mock out datetime in some tests so they don't fail occasionally when they
 # run too slow. Use a fixed datetime for datetime.now(). DST change in

django/test/utils.py

@@ -2,6 +2,7 @@ from contextlib import contextmanager
 import logging
 import re
 import sys
+from threading import local
 import time
 import warnings
 from functools import wraps
@@ -441,6 +442,23 @@ 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._accepted = {}
+        trans_real._checked_languages = {}
+
+    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),