MarsSeed [1] filed a deletion request for cl-jupyter [2]: VCS package without proper suffix and missing pkgver() function. Development discontinued in 2018.
There is a renamed continuation fork, available on AUR: common-lisp-jupyter-git. Therefore no need to keep this one here (and it's also broken now). [1] https://aur.archlinux.org/account/MarsSeed/ [2] https://aur.archlinux.org/pkgbase/cl-jupyter/
