This extension is not distributed with Mercurial.
Author: JamesMills (prologic)
Status: This has been unmaintained for some time now. If someone would like to take this over, let me know.
Download site: https://bitbucket.org/prologic/hgtrac/raw/tip/hgtrac.py
Configure your .hgrc to enable the extension by adding following lines:
This extension is partially similar to HgTracHook.