News about StopIteration as a "sink state".

Misc/NEWS

@@ -6,6 +6,14 @@ Type/class unification and new-style classes
 
 Core and builtins
 
+- All standard iterators now ensure that, once StopIteration has been
+  raised, all future calls to next() on the same iterator will also
+  raise StopIteration.  There used to be various counterexamples to
+  this behavior, which could caused confusion or subtle program
+  breakage, without any benefits.  (Note that this is still an
+  iterator's responsibility; the iterator framework does not enforce
+  this.)
+
 - Ctrl+C handling on Windows has been made more consistent with
   other platforms.  KeyboardInterrupt can now reliably be caught,
   and Ctrl+C at an interative prompt no longer terminates the