Hi Cristian,

>  I don't want to have three ways to load certificates, especially when it involves more C code.

I think this (more C code) is the primary and the *only* negative point against the current patch. And that seems necessary for the feature specific to OpenSSL. 

Not sure if you looked at the latest version (https://github.com/python/cpython/pull/2449/files) recently. 

The current patch does not deviate in-principle from the PEP 543.

It maintains the same API arguments ` SSLContext.load_cert_chain(certfile, keyfile=None, password=None)`

* We expect the migration of ssl module to newer ABC of PEP-543 not be one-to-one. We could foresee this API living. (And we haven't deprecated this API).

* The patch provides the feature along with plenty of tests that PEP-543 talks about (Loading of certs from memory).

* Has an implementation refactorable for OpenSSL-specific TLS backend (as one of the provider), that again will be useful to PEP-543 implementation.

These are the benefits in my opinion.

PEP-543 is important and seems like a *major effort*. The current patch might still be valuable and perhaps might be useful towards PEP-543 implementation. It deals only with certificates only.