3.4.2.5. Trac
Written in Python, Trac (http://www.edgewall.com/trac/) is an issue tracker with a few extra features thrown in. On top of all the usual issue-tracking features, it also includes a fairly good Wiki engine and a source control repository browser. Trac is written in Python and stores its issue-tracking data using SQLite. There's a branch of the code to support storage using PostgreSQL (and possibly other backends) and although the branch is currently incomplete there is work going on in this area. The repository browser built into Trac is for Subversion only.
Pros
Easy to installuses a single Python install script.
Very straightforward interface.
Cons
Stores data in SQLite or PostgreSQL, which probably isn't what you're using for your main application, so integration with the rest of your workflow can be tricky.
Only works with Subversion, and requires it.
Requires the ClearSilver templating engine.