Python Requests 'certificate Verify Failed' For A Specific Sni Certificate

I have been using the python requests framework for pretty much all my projects for many years now and haven't come across a problem like this. This happens only for the website ww

Solution 1:

... but the snippet above gives me the generic SSL failure exception ...

 ...'tls_process_server_certificate', 'certificate verify failed')],)",),))

Actually, this is not a generic SSL failure. It clearly fails because it could not verify the certificate. And the reason is not SNI vs. non-SNI since SNI is used by default in requests for a long time.

The reason is instead a misconfiguration of the server. From the SSLLabs report:

This server's certificate chain is incomplete. Grade capped to B.

 

Chrome/Firefox browsers open this site up, no problem ...

Desktop browsers usually work around successfully this type of common misconfiguration, for example by caching intermediate certificates from other connections and using these to fill in missing parts of the certificate chain. But if you try for example a Firefox with a fresh profile you'll get the same kind of SSL problems.