Fabric: 如何使用密码创建连接？

这是我的公钥出现在服务器上的时候：

>>> c = Connection(host=ip, user='root', port=22)
>>> c.run('uname -s')
Linux
<Result cmd='uname -s' exited=0>

这是从服务器中删除我的公钥时：

>>> c = Connection(host=ip, user='root', port=22)
>>> c.run('uname -s')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<decorator-gen-3>", line 2, in run
  File "/usr/local/lib/python2.7/dist-packages/fabric/connection.py", line 23, in opens
    self.open()
  File "/usr/local/lib/python2.7/dist-packages/fabric/connection.py", line 488, in open
    self.client.connect(**kwargs)
  File "/usr/local/lib/python2.7/dist-packages/paramiko/client.py", line 424, in connect
    passphrase,
  File "/usr/local/lib/python2.7/dist-packages/paramiko/client.py", line 691, in _auth
    self._transport.auth_publickey(username, key))
  File "/usr/local/lib/python2.7/dist-packages/paramiko/transport.py", line 1450, in auth_publickey
    return self.auth_handler.wait_for_response(my_event)
  File "/usr/local/lib/python2.7/dist-packages/paramiko/auth_handler.py", line 212, in wait_for_response
    raise e
AttributeError: '_RSAPrivateKey' object has no attribute 'sign'

如何将密码传递给Connection？ PS：我在新文档（2.0）中找不到它。