Default pyOpenSSL not compatible with current cryptography

[MatthijsBurgh]

See pyca/pyopenssl#1143

The default version of pyOpenSSL on ubuntu 20.04 installed by apt: is 19.0.0. Is it only compatible with cryptography<38.0.0. Though that was not defined at the time of release. When cryptography is installed via pip, it will break pyOpenSSL.

pyOpenSSL is used by the twisted server, therefore it breaks the webserver.

(cryptography is installed as a indirect dependency of xhtml2pdf)