[3.9] gh-90355: Add isolated flag if currently isolated (GH-92857) (GH-94570)

Co-authored-by: Carter Dodd <carter.dodd@gmail.com>
Co-authored-by: Éric <merwok@netwok.org>
Co-authored-by: Łukasz Langa <lukasz@langa.pl>
(cherry picked from commit c8556bcf)