/usr/lib/python2.7/dist-packages/gtk-2.0/dsextras.py is in python-gobject-2 2.28.6-10ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/python2.7/dist-packages/gtk-2.0/../../../../share/pyshared/gtk-2.0/dsextras.py