Add script-type _spkg_check package that installs tox, mock, pytest etc. #28998
Description
Following a suggestion by vbraun in #19680, this ticket adds a
_spkg_check package (type=script) that
- installs the Python packages
tox,mock,pytestviapipifSAGE_CHECK=true - does nothing otherwise.
The package _spkg_check can be added as a dependency of Python packages that use this standard testing infrastructure, for testing them if SAGE_CHECK=true.
The branch demonstrates this on the package pygments by adding an spkg-check.
If this approach is favored, probably the spkg nose, currently a dependency of cvxopt and networkx, could be removed.
Component: build
Branch/Commit: public/28998-check_dependencies_package @ 623cb21
Reviewer: Matthias Koeppe
Issue created by migration from https://trac.sagemath.org/ticket/28998