/usr/lib/python2.7/dist-packages/singlet/lens/base.py is in python-unity-singlet 0.2.2-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/python2.7/dist-packages/singlet/lens/../../../../../share/pyshared/singlet/lens/base.py