I'm trying to use SSL to validate clients connecting a an asyncio socket server by specifying CERT_REQUIRED and giving a `cafile` containing the client certificate to allow. client and server code attached.

Certificates are generated with:

openssl req -x509 -newkey rsa:2048 -keyout client.key -nodes -out client.cert -sha256 -days 100

openssl req -x509 -newkey rsa:2048 -keyout server.key -nodes -out server.cert -sha256 -days 100

Observed behavior with python 3.7.5 and openSSL 1.1.1d
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When the client tries to connect without specifying a certificate, the call to asyncio.open_connection succeeds, but the received socket is closed right away, or to be more exact an EOF is received.

Observed behavior with python 3.7.4 and openSSL 1.0.2t
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When the client tries to connect without specifying a certificate, the call to asyncio.open_connection fails.

Expected behavior
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I'm not sure which behavior is to be considered the expected one, although I would prefer to connection to fail directly instead of returning a dead client. Wouldn't it be better to have only one behavior?

Note that when disabling TLSv1.3, the connection does fail to open:
ctx.maximum_version = ssl.TLSVersion.TLSv1_2

This can be reproduces on all latest releases of 3.6, 3.7, and 3.8 (which all have openssl 1.1.1d in my case)

I'm unassigning myself. This seems to be an asyncio-specific behavior.