Is it possible to subclass Lock() objects in Python? If not, other ways to debug deadlock?

So, I've got a multithreaded python program, which is currently suffering from deadlock. I was going to log lock acquiring by subclassing threading.Lock objects:

import traceback
class DebugLock(threading.Lock):
    def acquire(self):
        print >>sys.stderr, "acquired", self
        #traceback.print_tb
        threading.Lock.acquire(self)  
    def release(self):
        print >>sys.stderr, "released", self
        #traceback.print_tb
        threading.Lock.release(self)  

When I try to run the program, I get the following error:

    class DebugLock(threading.Lock):
TypeError: Error when calling the metaclass bases
    cannot create 'builtin_function_or_method' instances  

So, my question is twofold:

1. Is it possible to subclass Lock objects to do what I'm doing?

2. If not, what is the best way to debug deadlock in python?

Note: I'm not writing any Python extension. There's a similar question: How to debug deadlock with python? However, it deals with compiling C++ code and using GDB, which I can't do since my code is pure python.