/usr/lib/x86_64-linux-gnu/libtclreadline.so is in tcl-tclreadline 2.1.0-15+deb9u1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libtclreadline-2.1.0.so
/usr/lib/x86_64-linux-gnu/libtclreadline-2.1.0.so