Issue #25764: Merge subprocess fix from 3.5

diff --cc Misc/NEWS
index f4e7e54bc03d99aee8b333e66b25547a55b1bf8c,4cca7a2a9d2894ca55d0eb22a61b8c57154923f4..daadfdf188c7ada0f47385e238d9ec1f315a298b
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -109,9 -22,9 +109,12 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #25764: In the subprocess module, preserve any exception caused by
+   fork() failure when preexec_fn is used.
+ 
 +- Issue #25771: Tweak the exception message for importlib.util.resolve_name()
 +  when 'package' isn't specified but necessary.
 +
  - Issue #6478: _strptime's regexp cache now is reset after changing timezone
    with time.tzset().