SAGE_ROOT/tox.ini: Make tox -p auto and tox --listenvs useful again #32764
Description
(from #29146)
tox does not actually understand the nested braces used in envlist.
https://groups.google.com/g/sage-devel/c/NU-xlUTIIdE/m/Q14HiKvNAgAJ
CC: @jhpalmieri @kliem
Component: porting
Author: Matthias Koeppe
Branch/Commit: 47a2b42
Reviewer: John Palmieri
Issue created by migration from https://trac.sagemath.org/ticket/32764