/usr/lib/ghc-doc/hoogle/libghc-clientsession-doc.txt is in libghc-clientsession-doc 0.9.1.2-3build9.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-clientsession-doc/html/clientsession.txt