Check if we can remove the pyOpenSSL dependency

[glevco]

The pypi page for pyOpenSSL states:

Note: The Python Cryptographic Authority strongly suggests the use of pyca/cryptography where possible. If you are using pyOpenSSL for anything other than making a TLS connection you should move to cryptography and drop your pyOpenSSL dependency.

Since we already use cryptography, we should check if we can use it exclusively and remove that other dependency.