TLS does not work

According to the documentation, zun provides [ssl] section that allows to enable TLS.

I have defined cert_file and key_file but seems like they are not passed correctly to websockifyserver:

DEBUG zun.websocket.websocketproxy [-] exception vmsg /openstack/venvs/zun-26.1.0.dev111/lib/python3.8/site-packages/websockify/websockifyserver.py:606
ERROR zun.websocket.websocketproxy Traceback (most recent call last):
ERROR zun.websocket.websocketproxy File "/openstack/venvs/zun-26.1.0.dev111/lib/python3.8/site-packages/websockify/websockifyserver.py", line 663, in top_new_client
ERROR zun.websocket.websocketproxy client = self.do_handshake(startsock, address)
ERROR zun.websocket.websocketproxy File "/openstack/venvs/zun-26.1.0.dev111/lib/python3.8/site-packages/websockify/websockifyserver.py", line 559, in do_handshake
ERROR zun.websocket.websocketproxy context.load_cert_chain(certfile=self.cert, keyfile=self.key, password=self.key_password)
ERROR zun.websocket.websocketproxy IsADirectoryError: [Errno 21] Is a directory

During my initial troubleshooting, I noticed that these variables have following values:

self.cert = /
self.key = None

It's not a big issue for zun-api, because TLS may be enabled on uWSGI, but for zun-wsproxy I couldn't find any way to enable TLS.

I'm using master branch.