Python 2 is EOL at the end of 2019.

We need to convert all of our Python components – core, circulation, metadata, and library_registry – to Python 3.

We need to be able to build Docker images that use Python 3, and internally to NYPL, we need to be able to deploy Python 3 code through Puppet and Jenkins (https://jira.nypl.org/browse/SEB-1553 covers this).