Fix compatibility with Python 2.5.
Review Request #4260 — Created June 25, 2013 and submitted
Fix compatibility with Python 2.5. The latest RB release broke Python 2.5 compatibility, due to using @property.setter, which is only in 2.6+. This fixes it to be compatible with 2.5. It also sets our markdown dependency to hard-code a working version for Python 2.5.
Installed and ran unit tests on 2.5.
