etcd connection failed in client

[chanhz]

Hi, I met a error while using ca to build a client:

>>> import etcd3 as etcd
>>> client = etcd.client(host='127.0.0.1', port=2379, ca_cert="/etc/etcd/pki/apiserver-etcd-client.crt", cert_key="/etc/etcd/pki/apiserver-etcd-client.key", cert_cert="/etc/etcd/pki/ca.crt")
>>> client.get('foo')
Traceback (most recent call last):
  File "<input>", line 1, in <module>
    client.get('foo')
  File "/root/go/src/github.com/kubernetes-sigs/etcdadm/etcd3/lib/python3.8/site-packages/etcd3/client.py", line 283, in get
    range_response = self.get_response(key, **kwargs)
  File "/root/go/src/github.com/kubernetes-sigs/etcdadm/etcd3/lib/python3.8/site-packages/etcd3/client.py", line 48, in handler
    _translate_exception(exc)
  File "/root/go/src/github.com/kubernetes-sigs/etcdadm/etcd3/lib/python3.8/site-packages/etcd3/client.py", line 32, in _translate_exception
    raise exception
etcd3.exceptions.ConnectionFailedError: etcd connection failed

What make me confuse is that etcdctl works well, but the lib failed.