Issue #12157: pool.map() does not handle empty iterable correctly

Initial patch by mouad
diff --git a/Misc/NEWS b/Misc/NEWS
index d8d5199..b832384 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -67,6 +67,9 @@
 Library
 -------
 
+- Issue #12157: Make pool.map() empty iterables correctly.  Initial
+  patch by mouad.
+
 - Issue #14962: Update text coloring in IDLE shell window after changing
   options.  Patch by Roger Serwy.