Add Misc/NEWS entry and relevant doc change for issue 10271.
diff --git a/Misc/NEWS b/Misc/NEWS
index 3301d3f..a456bf3 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,8 @@
 Core and Builtins
 -----------------
 
+- Issue #10271: Allow warnings.showwarning() be any callable.
+
 - Issue #11627: Fix segfault when __new__ on a exception returns a non-exception
   class.