Poetry uses an isolated pep517 compliant environment to build wheels in. It seems that this environment breaks the cryptography 2.3 setup.py logic when building the wheels and it ends up not building any of the shared libraries. I assume this is because cryptography 2.3 is so old, that pep517 was new at the time and was not as well adopted.

A workaround is to use pip to install which will still install without enforcing pep517 requirements.