fixed pep8 error
diff --git a/tests/test_x509_ext.py b/tests/test_x509_ext.py
index 75fb914..043aaa7 100644
--- a/tests/test_x509_ext.py
+++ b/tests/test_x509_ext.py
@@ -869,7 +869,7 @@
             x509.load_der_x509_certificate,
             backend
         )
-        ext = cert.extensions.get_extension_for_oid(
+        cert.extensions.get_extension_for_oid(
             ExtensionOID.BASIC_CONSTRAINTS
         )
         assert ext is not None