diff --git a/nova/tests/unit/test_api_validation.py b/nova/tests/unit/test_api_validation.py
index c71266c3ce..cc5d48c7fc 100644
--- a/nova/tests/unit/test_api_validation.py
+++ b/nova/tests/unit/test_api_validation.py
@@ -14,7 +14,6 @@
 
 import copy
 import re
-import sys
 
 import fixtures
 from jsonschema import exceptions as jsonschema_exc
@@ -444,7 +443,7 @@ class PatternPropertiesTestCase(APIValidationTestCase):
         # Note(jrosenboom): This is referencing an internal python error
         # string, which is no stable interface. We need a patch in the
         # jsonschema library in order to fix this properly.
-        if sys.version[:3] in ['3.5', '3.6', '3.7']:
+        if six.PY3:
             detail = "expected string or bytes-like object"
         else:
             detail = "expected string or buffer"