All variables should use underscore separation. Try to avoid abbreviation.

ex:
```
security_descriptor 
dacl
```

My bad for not spotting this at the first review. I just did the review for the singleton part.

-----

It would be nice if _adjustPrivilege would we written as a context manager and avoid the try/finally:

```
with self._adjustPrivilege(
        win32security.SE_TAKE_OWNERSHIP_NAME, 
        win32security.SE_RESTORE_NAME,
        ):
    # code here
```

--------

Since we are now really using _adjustPrivilege , we need a dedicated test for it... or a test for the _adjustPrivilege as a context manager. (see runAsUser context manager) or ask if need help.