Update os/os.test.py

Co-authored-by: Sebastien Binet <[email protected]>

Author: glaukiol1

os/os.test.py

@@ -44,7 +44,7 @@ def _fail(test_name):
 
 if os.error == OSError:
     _pass("os.error == OSError")
-    passed_tests = passed_tests + 1
+    passed_tests += 1
 else:
     _fail("os.error == OSError")
     failed += 1