pyopenssl version 0.14 and cryptography version 1.4 lead to the following run-time error:

I/python (13519): File "/home/enoch/.local/share/python-for-android/dists/gsld/private/lib/python2.7/site-packages/OpenSSL/crypto.py", line 1882, in b64_encode
I/python (13519): AttributeError: 'module' object has no attribute 'CRYPTO_free'

Current solution: Use cryptography version 1.3 as it defines 'CRYPTO_free'