Strange Python setuptools installed by default

Hi,

I recently fixed a failing test that seemed to uncover some strange stuff in CircleCI’s Python installation. I found that upgrading setuptools failed unless I removed two existing previous installations.

Failing test: https://circleci.com/gh/openaddresses/machine/202

Fixed test: https://circleci.com/gh/openaddresses/machine/213

What’s going on here? Is this a bug?