>>> db.create_collection('foobar', max=False, capped=False, size=0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pymongo/database.py", line 245, in create_collection
    return Collection(self, name, **opts)
  File "pymongo/collection.py", line 108, in __init__
    self.__create(kwargs)
  File "pymongo/collection.py", line 119, in __create
    self.__database.command("create", self.__name, **options)
  File "pymongo/database.py", line 388, in command
    result = self["$cmd"].find_one(command, **extra_opts)
  File "pymongo/collection.py", line 516, in find_one
    for result in self.find(spec_or_id, *args, **kwargs).limit(-1):
  File "pymongo/cursor.py", line 778, in next
    if len(self.__data) or self._refresh():
  File "pymongo/cursor.py", line 729, in _refresh
    self.__uuid_subtype))
  File "pymongo/cursor.py", line 686, in __send_message
    self.__uuid_subtype)
  File "pymongo/helpers.py", line 104, in _unpack_response
    error_object["$err"])
pymongo.errors.OperationFailure: database error: unrecognized command: $query

Sun Sep  9 14:48:58 ./mongos db version v2.0.6, pdfile version 4.5 starting (--help for usage)
...
Sun Sep  9 14:49:59 [conn2] Request::process ns: foo.$cmd msg id:2019554530 attempt: 0
Sun Sep  9 14:49:59 [conn2] single query: foo.$cmd  { $query: { create: "foobar", max: false, capped: false, size: 0.0 }, $readPreference: { mode: "primary" } }  ntoreturn: -1 options : 0
Sun Sep  9 14:49:59 [conn2] User Assertion: 13390:unrecognized command: $query