bpo-45234: Fix FileNotFound exception raised instead of IsADirectoryError in shutil.copyfile() (GH-28421) (GH-28508)

This was a regression from fixing BPO-43219.
(cherry picked from commit b7eac52b466f697d3e89f47508e0df0196a98970)

Co-authored-by: andrei kulakov <andrei.avk@gmail.com>