/usr/share/doc/pybind11-doc/html/_static/css/theme.css is in pybind11-doc 2.0.1-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/pybind11-doc/html/_static/css/../../../../../sphinx_rtd_theme/static/css/theme.css