Fix issue #6973: When we know a subprocess.Popen process has died, do

not allow the send_signal(), terminate(), or kill() methods to do
anything as they could potentially signal a different process.

diff --cc Lib/subprocess.py
Simple merge

diff --cc Misc/NEWS
index f0ade032aceb50cbfc1057239208ec75faeead64,2d0755f931d598478434541edc35cf3d4b815ba8..41ed26213bc045689cc16f87b4d04181a653ec8d
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -70,6 -106,12 +70,10 @@@ Core and Builtin
  Library
  -------
  
 -- Issue #25578: Fix (another) memory leak in SSLSocket.getpeercer().
 -
+ - Issue #6973: When we know a subprocess.Popen process has died, do
+   not allow the send_signal(), terminate(), or kill() methods to do
+   anything as they could potentially signal a different process.
+ 
  - Issue #25590: In the Readline completer, only call getattr() once per
    attribute.