Bug #1588287: fix invalid assertion for `1,2` in debug builds.

Will backport
diff --git a/Misc/NEWS b/Misc/NEWS
index 2ed9371..0527d83 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,8 @@
 Core and builtins
 -----------------
 
+- Bug #1588287: fix invalid assertion for `1,2` in debug builds.
+
 - Bug #1576657: when setting a KeyError for a tuple key, make sure that
   the tuple isn't used as the "exception arguments tuple".