/usr/lib/ghc-doc/hoogle/libghc-exact-pi-doc.txt is in libghc-exact-pi-doc 0.4.1.2-3build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-exact-pi-doc/html/exact-pi.txt