(from #33546)

When running doctests via sage --pytest (added in #33546), there are many failed tests due to some issues with assumptions and/or symbolic variables and/or deprecation warnings.
To see examples of these failures, run pytest on

src/sage/manifolds/differentiable/examples/sphere.py
src/sage/manifolds/utilities.py
src/sage/manifolds/chart.py

UPDATE - deprecation warnings are OK, thanks to 92bbf1d in comment:10

CC: @tobiasdiez

Component: doctest framework

Author: Dima Pasechnik, Tobias Diez

Branch/Commit: public/build/pytest-github-action @ 92bbf1d

Issue created by migration from https://trac.sagemath.org/ticket/33826