Comment 2 for bug 1560060

So cryptography has a utility to deprecate modules and it was missing the ability to use `__delattr__` appropriately until https://github.com/pyca/cryptography/pull/2845. This means we have to wait for a version that is not 1.3 with that fix. We should probably update global-requirements to blacklist 1.3 until that fix is released in either a patch release for 1.3 or in 1.4