This is an install-requires of notebook.

In #26919 we did not add it, but if we let Python dependencies play out (for example as in #30913), it gets pulled in by sagelib via ipywidgets (see also #31278).

CC: @jcamp0x2a @slel @kcrisman @dimpase @jhpalmieri @tobiasdiez

Component: packages: standard

Author: Matthias Koeppe

Branch: 45e5cd2

Reviewer: Jonathan Kliem

Issue created by migration from https://trac.sagemath.org/ticket/31279