/usr/share/postgresql/9.5/extension/ is in postgresql-plpython-9.5 9.5.2-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/postgresql/9.5/extension/hstore_plpython2u--1.0.sql
/usr/share/postgresql/9.5/extension/hstore_plpython2u.control
/usr/share/postgresql/9.5/extension/hstore_plpythonu--1.0.sql
/usr/share/postgresql/9.5/extension/hstore_plpythonu.control
/usr/share/postgresql/9.5/extension/ltree_plpython2u--1.0.sql
/usr/share/postgresql/9.5/extension/ltree_plpython2u.control
/usr/share/postgresql/9.5/extension/ltree_plpythonu--1.0.sql
/usr/share/postgresql/9.5/extension/ltree_plpythonu.control
/usr/share/postgresql/9.5/extension/plpython2u--1.0.sql
/usr/share/postgresql/9.5/extension/plpython2u--unpackaged--1.0.sql
/usr/share/postgresql/9.5/extension/plpython2u.control
/usr/share/postgresql/9.5/extension/plpythonu--1.0.sql
/usr/share/postgresql/9.5/extension/plpythonu--unpackaged--1.0.sql
/usr/share/postgresql/9.5/extension/plpythonu.control