I discovered the root cause of the issue by comparing the output of `pip freeze` on both servers.
Apparently on the upgraded server cryptography-1.9 was installed in `/usr/local/python2.7/dist-packages`, while overriding python-cryptography package.
Running `sudo pip uninstall cryptography` resolves the issue.
I discovered the root cause of the issue by comparing the output of `pip freeze` on both servers.
Apparently on the upgraded server cryptography-1.9 was installed in `/usr/local/ python2. 7/dist- packages` , while overriding python-cryptography package.
Running `sudo pip uninstall cryptography` resolves the issue.