Fix caching problems in unit tests

src/tests/base/test_cache.py

@@ -1,12 +1,18 @@
 import random
 
 from django.core.cache import cache as django_cache
-from django.test import TestCase
+from django.test import TestCase, override_settings
 from django.utils.timezone import now
 
 from pretix.base.models import Event, Organizer
 
 
+@override_settings(CACHES={
+    'default': {
+        'BACKEND': 'django.core.cache.backends.locmem.LocMemCache',
+        'LOCATION': 'unique-snowflake',
+    }
+})
 class CacheTest(TestCase):
     """
     This test case tests the invalidation of the event related