> First it’s necessary to install OCaml and Opam. Opam is the default package manager for OCaml projects.

    $ sudo apt install opam

    ...list of packages, including several python 2 packages, darcs, and mercurial ---

    After this operation, 451 MB of additional disk space will be used.
    Do you want to continue? [Y/n] n
    Abort.

Python 2 ? In 2021?

Also, darcs? And mercurial?