Estoy trabajando con el módulo python pyttsx para texto a voz y cuando ejecuto el código, aparece este error:

     File "Practice_File.py", line 2, in <module>
     engine = pyttsx.init()
     File "/Library/Python/2.7/site-packages/pyttsx/__init__.py",
     line 39, in init
     eng = Engine(driverName, debug)
     File "/Library/Python/2.7/site-packages/pyttsx/engine.py", line
     45, in __init__
     self.proxy = driver.DriverProxy(weakref.proxy(self), driverName,
     debug)
     File "/Library/Python/2.7/site-packages/pyttsx/driver.py", line
     64, in __init__
     self._module = __import__(name, globals(), locals(), [driverName])
     File "/Library/Python/2.7/site-packages/pyttsx/drivers
     /nsss.py", line 26, in <module>
     class NSSpeechDriver(NSObject):
     objc.BadPrototypeError: Objective-C expects 1 arguments, Python
     argument has 2 arguments for <unbound selector initWithProxy of
     NSSpeechDriver at 0x107592e68>

Aquí está mi código de Python:

    import pyttsx
    engine = pyttsx.init()
    engine.say('Good morning.')
    engine.runAndWait()

¿Alguna idea sobre cómo solucionar este problema? Gracias.