/usr/share/doc/python-distributed-doc/html/_static/css/theme.css is in python-distributed-doc 1.20.2+ds.1-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/python-distributed-doc/html/_static/css/../../../../../sphinx_rtd_theme/static/css/theme.css