Summary:
Some people want to use getdeps with Python 2.7. This looks easy to do, so take a step toward Python 2.7 support by fixing getdeps' tests when run with Python 2.7.

For Python 3, this diff should not change behavior.

This diff should address https://github.com/facebook/bistro/issues/35.

Reviewed By: snarkmaster

Differential Revision: D16435667

fbshipit-source-id: f5c262b12995b609263341c4de26dac7f9b12b70