diff --git a/tests/unit/utils.py b/tests/unit/utils.py
index 4f7c8ec4..ac9aefdb 100644
--- a/tests/unit/utils.py
+++ b/tests/unit/utils.py
@@ -503,7 +503,7 @@ class FakeKeystone(object):
         self.endpoint = endpoint
         self.token = token
 
-    class _Client():
+    class _Client(object):
         def __init__(self, endpoint, token, **kwargs):
             self.auth_token = token
             self.endpoint = endpoint
diff --git a/tox.ini b/tox.ini
index e5b207c6..1008f5db 100644
--- a/tox.ini
+++ b/tox.ini
@@ -45,9 +45,10 @@ commands=
 # H102 -> apache2 license exists
 # H103 -> license is apache
 # H201 -> no bare excepts
+# H238 -> old style classes are deprecated and not available in python3
 # H501 -> don't use locals() for str formatting
 # H903 -> \n not \r\n
 ignore = H
-select = H102, H103, H201, H501, H903
+select = H102, H103, H201, H238, H501, H903
 show-source = True
 exclude = .venv,.tox,dist,doc,*egg