/usr/lib/python2.7/dist-packages/sphinxcontrib/blockdiag.py is in python-sphinxcontrib.blockdiag 1.3.0-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/python2.7/dist-packages/sphinxcontrib/../../../../share/pyshared/sphinxcontrib/blockdiag.py