Upgrade cryptography to 2.7
Upgrade cryptography to 2.7

In #3139, cryptography was upgraded from 2.1.4 to 2.2.1 to satisfy a
requirement of pyOpenSSL 19.0.0. However, upgrading to that version of
cryptography did not fix the security vulnerability, which was patched
in 2.3.1. The library is updated again here to remedy the vulnerability.

Refs #3101

WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed