AttributeError: module 'lib' has no attribute 'Cryptography_HAS_TLSEXT_HOSTNAME'

I’ve used the python:3.7.6-slim-stretch docker image for almost one year. Just today I got this strange issue (with pyOpenSSL==17.5.0):

>>> from OpenSSL import *
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python3.7/site-packages/OpenSSL/__init__.py", line 8, in <module>
from OpenSSL import crypto, SSL
File "/usr/local/lib/python3.7/site-packages/OpenSSL/SSL.py", line 673, in <module>
_lib.Cryptography_HAS_TLSEXT_HOSTNAME, "SNI not available"
AttributeError: module 'lib' has no attribute 'Cryptography_HAS_TLSEXT_HOSTNAME'

The only versions that work correctly are pyOpenSSL==19.1.0 and pyOpenSSL==20.0.0.

[reaperhulk]

Upgrading pyopenssl will resolve this error. Cryptography removed the binding because pyopenssl 19.1 and above no longer depend on it.

[mhaggag]

We had this error pop up on one of servers today, and after comparing the dependent packages for pyopenssl on working servers vs the non-working server, I found that reverting cryptography from 3.3 to 3.2 (using pip3 install cryptography==3.2) works around this error until we figure out what’s going on.