Fix tests

Author: fsbraun

run_tests.py

@@ -7,7 +7,9 @@
 from django.test.utils import get_runner
 
 
-def run(argv):
+def run(argv=None):
+    if argv is None:
+        argv = ["tests"]
     tests = argv[1:] if len(argv) > 1 else ["tests"]
     os.environ["DJANGO_SETTINGS_MODULE"] = "tests.test_settings"
     django.setup()