AttributeError raised when use_greenlets=True is specified without gevent

>>> import pymongo

>>> c = pymongo.MongoClient(use_greenlets=True)

Traceback (most recent call last):

  File "<stdin>", line 1, in ?

  File "pymongo/mongo_client.py", line 331, in __init__

    wait_queue_multiple=self.__wait_queue_multiple)

  File "pymongo/pool.py", line 145, in __init__

    raise ConfigurationError(

pymongo.errors.ConfigurationError: The Gevent module is not available. Install the gevent package from PyPI.

>>> 

Exception exceptions.AttributeError: "Pool instance has no attribute 'sockets'" in <bound method Pool.__del__ of <pymongo.pool.Pool instance at 0x722878>> ignored