/usr/share/common-lisp/systems/postmodern.asd is in cl-postmodern 20170403-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/common-lisp/systems/../source/postmodern/postmodern.asd
/usr/share/common-lisp/systems/../source/postmodern/postmodern.asd