GH-93112: Fix missing ResourceDenied import in test_urllib2net (GH-93113)

The code was moved out of test.support in
311110abcd8ab648dbf1803e36a8ba5d93fa019b (GH-20812), thus making
ResourceDenied undefined.
(cherry picked from commit 37c9a351b15c3fc4fcdca5dcb9ce19e51d7d2dd7)

Co-authored-by: Florian Bruhin <me@the-compiler.org>