Pywikibot faced some unicode issues in 2010-11 experienced with interwiki.py primarily.
This task is created to capture some of the history of that, as it is a key factor in some versions being listed as unsupported on the support matrix at https://www.mediawiki.org/wiki/Manual:Pywikibot/Version_table
Python issue 10254 was initially raised as http://sourceforge.net/p/pywikipediabot/bugs/1246 , affecting Python 2.6.6, Python 2.7.0 and Python 3.0. The fix was merged into 2.6.7, Python 2.7.2, but was not backported into 2.7.1, and into Python 3 long before the lowest Pywikibot supported version of Python 3.3. Therefore this bug affects Pywikibot support on Python 2.6.6, Python 2.7.0 and Python 2.7.1.
http://sourceforge.net/p/pywikipediabot/bugs/1382/ was a related issue, but the solution was "upgrade to 2.7.2", so there is little information about the cause or solution. It is listed as the reason that Python 2.5 was de-supported.