Fabric: AttributeError: 'str' 对象在使用自定义 connect_kwargs 和 key_filename 选项时没有属性 'extend'

使用带有key_filename选项的自定义connect_kwargs时，如下所示：

    config = fabric.config.Config()
    print("Connecting with ssh/config")
    with fabric.Connection(
        host=instancePrivateIp,
        user='ec2-user',
        config=config,
        connect_kwargs={
            "key_filename": keyFileName,
        }) as c_instance:

我得到一个AttributeError ：

  File "/home/dumontj/Projects/ami-builder/ami_builder/customization.py", line 26, in do_bash_customization
    "key_filename": keyFileName,
  File "/home/dumontj/.local/share/virtualenvs/ami-builder-jbdgQc96/lib/python3.7/site-packages/fabric/connection.py", line 450, in __init__
    self.connect_kwargs = self.resolve_connect_kwargs(connect_kwargs)
  File "/home/dumontj/.local/share/virtualenvs/ami-builder-jbdgQc96/lib/python3.7/site-packages/fabric/connection.py", line 490, in resolve_connect_kwargs
    connect_kwargs["key_filename"].extend(
AttributeError: 'str' object has no attribute 'extend'

文档指定key_filename应该作为字符串给出，但我发现如果你真的给它一个列表它可以工作：

    with fabric.Connection(
        host=instancePrivateIp,
        user='ec2-user',
        config=config,
        connect_kwargs={
            "key_filename": [keyFileName,],
        }) as c_instance:

如果这是想要的语法，我可以通过 PR 更新文档（参见 https://github.com/fabric/fabric/blob/2.0/fabric/connection.py#L234）。 否则，我可以更改fabric/connection.py以检查是否已经存在条目，然后在必要时将其转换为列表。