错误：无法通过ssh连接到主机

我正在尝试学习ansible，并遵循o'riley Ansible Up和跑步书。

在本书的入门部分，它要求我安装ansible，virtualbox和vagrant，然后通过CLI运行：

vagrant init ubuntu/trusty64

vagrant up

之后，我可以通过vagrant ssh或通过以下方式将ssh进入VM：

ssh [email protected] -p 2222 -i /Users/XXX/playbooks/.vagrant/machines/default/virtualbox/private_key

接下来是创建如下所示的hosts文件：

testserver ansible_ssh_host=127.0.0.1 ansible_ssh_port=2222 \ ansible_ssh_user=vagrant \ ansible_ssh_private_key_file=.vagrant/machines/default/virtualbox/private_key

最后正在运行此命令：

ansible testserver -i主机-m ping

这让我：

testserver | UNREACHABLE! => {
    "changed": false,
    "msg": "Failed to connect to the host via ssh.",
    "unreachable": true
}

添加-vvv让我得到：

No config file found; using defaults
<127.0.0.1> ESTABLISH SSH CONNECTION FOR USER: None
<127.0.0.1> SSH: EXEC ssh -C -q -o ControlMaster=auto -o ControlPersist=60s -o Port=2222 -o KbdInteractiveAuthentication=no -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey -o PasswordAuthentication=no -o ConnectTimeout=10 -o ControlPath=/Users/XXX/.ansible/cp/ansible-ssh-%h-%p-%r 127.0.0.1 '/bin/sh -c '"'"'( umask 77 && mkdir -p "` echo $HOME/.ansible/tmp/ansible-tmp-1468541275.7-255802522359895 `" && echo ansible-tmp-1468541275.7-255802522359895="` echo $HOME/.ansible/tmp/ansible-tmp-1468541275.7-255802522359895 `" ) && sleep 0'"'"''
testserver | UNREACHABLE! => {
    "changed": false,
    "msg": "Failed to connect to the host via ssh.",
    "unreachable": true
}

我尝试修改hosts文件中的ansible_ssh_private_key_file以指向私钥的完整路径，但是仍然无法正常工作：

ansible testserver -i hosts -m ping -vvv
No config file found; using defaults
<127.0.0.1> ESTABLISH SSH CONNECTION FOR USER: None
<127.0.0.1> SSH: EXEC ssh -C -q -o ControlMaster=auto -o ControlPersist=60s -o Port=2222 -o KbdInteractiveAuthentication=no -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey -o PasswordAuthentication=no -o ConnectTimeout=10 -o ControlPath=/Users/XXX/.ansible/cp/ansible-ssh-%h-%p-%r 127.0.0.1 '/bin/sh -c '"'"'( umask 77 && mkdir -p "` echo $HOME/.ansible/tmp/ansible-tmp-1468541370.61-137685863794569 `" && echo ansible-tmp-1468541370.61-137685863794569="` echo $HOME/.ansible/tmp/ansible-tmp-1468541370.61-137685863794569 `" ) && sleep 0'"'"''
testserver | UNREACHABLE! => {
    "changed": false,
    "msg": "Failed to connect to the host via ssh.",
    "unreachable": true
}

这是我的Ansible版本：

ansible --version ansible 2.1.0.0配置文件=配置的模块搜索路径=默认（无覆盖）

任何人都有任何想法，为什么ansible无法连接到我无所事事的VM？