heroku/heroku-buildpack-python — pull request #136 by bennylope (2014-05-07 23:22:52+00:00)
Title: Update pip to v1.5.5

Updating to pip locally (and then testing using this buildpack update) solved the [`AttributeError: 'str' object has no attribute 'rollback'`](https://github.com/pypa/pip/issues/1350) pip issue present in 1.5.4.