/usr/lib/python2.7/dist-packages/sphinxcontrib_blockdiag-1.3.0-nspkg.pth 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/../../../share/pyshared/sphinxcontrib_blockdiag-1.3.0-nspkg.pth