Coverage remained the same when pulling fad968c90306de15a8a6947af8e936b6c546cf00 on atodorov:fix_format into 8181f6d3dcd2972adcd569d779accf0cac28c549 on gak:develop.
Thanks for this @atodorov .. I did intend this project to be for 2.7 and onwards, but since you did the work, I'm happy to accept. Also sorry for the slow acceptance.
This fix makes it possible to execute: pycallgraph graphviz -o calls.png -f png -- ./myscript.py
on Python 2.6.6.
There are probably other places which need patches but haven't bumped into them yet!