Import Error: libffi.so.6: cannot open shared object file: No such file or directory

TL;DR This is the solution when Jupyter notebook fails to start because the file libffi.so.6 could not be imported. In my environment, pyenv was used to manage the version of python, so it is for those who manage it in the same way.

Error

% jupyter notebook
Import Error: libffi.so.6: cannot open shared object file: No such file or directory

Solution

From here [^ 1]

% pyenv version
i.j.k(set by $HOME/.pyenv/versions/i.j.k)
% pyenv install i.j.k
Installed Python-i.j.k to $HOME/.pyenv/versions/i.j.k

All you have to do is reinstall the version of Python you were using. You should now be able to boot.