Pywikibot was a sourceforce.net project: http://sourceforge.net/projects/pywikipediabot/
Bug numbers with a very high number probably refer to the old sourceforce.net tracking numbers, and were able to be found by manually constructing a URL to tracker.php. e.g. Special:Code/pywikipedia/8703 linked to https://sourceforge.net/support/tracker.php?aid=3081100 in the commit message, and Special:Code/pywikipedia/3614 referred to '1731008'. However as of November 2014, this no longer works.
These numbers can be made to work by using one of the following:
pywikibot-compat.externals was a project used in order to provide ways to install catimages.py dependencies: https://phabricator.wikimedia.org/diffusion/PWBO/browse/master/externals/
Replaced in the curse of the GSoC 2016 project Port catimages.py to pywikibot-core (T129611) by using pip (also conda on win) for the stable version and Docker (with Vagrant or other VMs) for the experimental development version. For more details about that, confer the project and the notes of the Meeting about handling non-pip packages / replace externals module.