Issue #21310: Fixed possible resource leak in failed open().

diff --cc Lib/test/test_io.py
Simple merge

diff --cc Misc/NEWS
index 99507251149ff56ab8bc252c3f4ac41a0960c752,29f5b61064425349af13823e7c1bc9ce7cb7c4a8..28474bb626f17c143976eb7493389a12a32475d9
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -92,9 -22,8 +92,11 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #21310: Fixed possible resource leak in failed open().
+ 
 +- Issue #21256: Printout of keyword args should be in deterministic order in
 +  a mock function call. This will help to write better doctests.
 +
  - Issue #21677: Fixed chaining nonnormalized exceptions in io close() methods.
  
  - Issue #11709: Fix the pydoc.help function to not fail when sys.stdin is not a