/usr/share/common-lisp/systems/yason.asd is in cl-yason 0.6.7-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/common-lisp/systems/../source/yason/yason.asd
/usr/share/common-lisp/systems/../source/yason/yason.asd