Issue #15501: Document exception classes in subprocess module.

Initial patch by Anton Barkovsky.
diff --git a/Misc/ACKS b/Misc/ACKS
index 1a094a1..4d8f13c 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -52,6 +52,7 @@
 Michael J. Barber
 Nicolas Bareil
 Chris Barker
+Anton Barkovsky
 Nick Barnes
 Quentin Barnes
 Richard Barran