This bug was fixed in the package python-cryptography - 2.1.4-1ubuntu1
--------------- python-cryptography (2.1.4-1ubuntu1) bionic; urgency=medium
* d/control: Add python-cffi to binary package dependencies (LP: #1752660).
-- Corey Bryant <email address hidden> Mon, 05 Mar 2018 14:37:41 -0500
This bug was fixed in the package python-cryptography - 2.1.4-1ubuntu1
---------------
python-cryptography (2.1.4-1ubuntu1) bionic; urgency=medium
* d/control: Add python-cffi to binary package dependencies (LP: #1752660).
-- Corey Bryant <email address hidden> Mon, 05 Mar 2018 14:37:41 -0500