environment/lib/python2.7/site-packages/IPython/external/ssh/tunnel.py
def _try_passwordless_paramiko(server, keyfile):
    """Try passwordless login with paramiko."""
    if paramiko is None:
        msg = "Paramiko unavaliable, "
        if sys.platform == 'win32':
            msg += "Paramiko is required for ssh tunneled connections on Windows."
        else:
            msg += "use OpenSSH."
        raise ImportError(msg)
    username, server, port = _split_server(server)
    client = paramiko.SSHClient()
    client.load_system_host_keys()
    client.set_missing_host_key_policy(paramiko.WarningPolicy())
    try:
        client.connect(server, port, username=username, key_filename=keyfile,
               look_for_keys=True)
    except paramiko.AuthenticationException:
        return False
    else:
        client.close()
        return True
def _try_passwordless_paramiko(server, keyfile):
    """Try passwordless login with paramiko."""
    if paramiko is None:
        msg = "Paramiko unavaliable, "
        if sys.platform == 'win32':
            msg += "Paramiko is required for ssh tunneled connections on Windows."
        else:
            msg += "use OpenSSH."
        raise ImportError(msg)
    username, server, port = _split_server(server)
    client = paramiko.SSHClient()
    client.load_system_host_keys()
    client.set_missing_host_key_policy(paramiko.WarningPolicy())
    try:
        client.connect(server, port, username=username, key_filename=keyfile,
               look_for_keys=True)
    except paramiko.AuthenticationException:
        return False
    else:
        client.close()
        return True
Try passwordless login with paramiko.