Decorator error: NoneType object is not callable

You should return the wrapper function itself, not its result:

def tsfunc(func):
    def wrappedFunc():
        print '%s() called' % func.__name__
        return func()
    return wrappedFunc   # Do not call the function, return a reference instead

Decorators replace the decorated item with the return value of the decorator:

@tsfunc
def foo():
    # ....

is equivalent to:

def foo():
    # ....
foo = tsfunc(foo)

which expands to (in your code):

foo = wrappedFunc()

so you were replacing the function foo with the result of the wrappedFunc() call, not with wrappedFunc itself.