(from #30448)

We add a tox environment that checks all of the static patterns that the patchbot checks - https://github.com/sagemath/sage-patchbot/blob/master/sage_patchbot/plugins.py#L601

This is so that developers can check style locally instead of going through endless cycles with the patchbot on trac.

This uses https://pypi.org/project/relint/

Example:

   sage -tox -e relint src/sage/plot/

Depends on #30410

CC: @fchapoton @jhpalmieri @tobiasdiez @tscrim @slel @kliem

Component: scripts

Author: Matthias Koeppe

Branch/Commit: 7cf9efe

Reviewer: Jonathan Kliem, Tobias Diez

Issue created by migration from https://trac.sagemath.org/ticket/30467