/usr/lib/tcltk/rivet2.1/packages/session/ is in libapache2-mod-rivet 2.1.3-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/tcltk/rivet2.1/packages/session/README.txt
/usr/lib/tcltk/rivet2.1/packages/session/session-class.tcl
/usr/lib/tcltk/rivet2.1/packages/session/session-create-mysql.sql
/usr/lib/tcltk/rivet2.1/packages/session/session-create-oracle.sql
/usr/lib/tcltk/rivet2.1/packages/session/session-create-postgresql.sql
/usr/lib/tcltk/rivet2.1/packages/session/session-create-sqlite.sql
/usr/lib/tcltk/rivet2.1/packages/session/session-demo.rvt
/usr/lib/tcltk/rivet2.1/packages/session/session-drop.sql
/usr/lib/tcltk/rivet2.1/packages/session/session-httpd.conf
/usr/lib/tcltk/rivet2.1/packages/session/session-purge-mysql.sql