We bundle a plugin for Bazaar that enables rbssh as a SSH transport.

This plugin has been the source of some frustration around broken unit

tests, and potentially issues in certain production environments.
The plugin made use of a Django import, just to get access to six, for

the sole purpose of six.text_type. The problem was, if Bazaar was

installed system-wide, and Review Board was installed in a virtualenv,

SSH operations would fail. bzr locally would invoke bzr on the other

side of the SSH connection, but outside of the virtualenv, and the

Django import could fail.
This import isn't really useful. It's easy enough to %-format the

number we wanted into a string. This change does that, simplifying the

code and preventing this common problem.

Encountered this frequently with unit tests. They now pass.