>>> from pymongo.driver_info import DriverInfo
>>> client = MongoClient(driver=DriverInfo(name='s'*512))
>>> client.admin.command('isMaster')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pymongo/database.py", line 730, in command
    read_preference, session) as (sock_info, slave_ok):
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/contextlib.py", line 17, in __enter__
    return self.gen.next()
  File "pymongo/mongo_client.py", line 1301, in _socket_for_reads
    with self._get_socket(server, session) as sock_info:
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/contextlib.py", line 17, in __enter__
    return self.gen.next()
  File "pymongo/mongo_client.py", line 1223, in _get_socket
    self.__all_credentials, checkout=exhaust) as sock_info:
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/contextlib.py", line 17, in __enter__
    return self.gen.next()
  File "pymongo/pool.py", line 1126, in get_socket
    sock_info = self._get_socket_no_auth()
  File "pymongo/pool.py", line 1178, in _get_socket_no_auth
    sock_info = self.connect()
  File "pymongo/pool.py", line 1093, in connect
    sock_info.ismaster(self.opts.metadata, None)
  File "pymongo/pool.py", line 516, in ismaster
    ismaster = IsMaster(self.command('admin', cmd, publish_events=False))
  File "pymongo/pool.py", line 614, in command
    user_fields=user_fields)
  File "pymongo/network.py", line 167, in command
    parse_write_concern_error=parse_write_concern_error)
  File "pymongo/helpers.py", line 159, in _check_command_response
    raise OperationFailure(msg % errmsg, code, response)
pymongo.errors.OperationFailure: The client metadata document must be less then or equal to 512bytes