py: Add MP_OBJ_STOP_ITERATION and make good use of it.

Also make consistent use of MP_OBJ_NOT_SUPPORTED and MP_OBJ_NULL.
This helps a lot in debugging and understanding of function API.

1 files changed, 2 insertions, 2 deletions

diff --git a/py/objgetitemiter.c b/py/objgetitemiter.c
index f848415b8..faa8321c3 100644
--- a/py/objgetitemiter.c
+++ b/py/objgetitemiter.c
@@ -26,8 +26,8 @@ STATIC mp_obj_t it_iternext(mp_obj_t self_in) {
     } else {
         // an exception was raised
         if (mp_obj_get_type(nlr.ret_val) == &mp_type_StopIteration) {
-            // return MP_OBJ_NULL instead of raising StopIteration
-            return MP_OBJ_NULL;
+            // return MP_OBJ_STOP_ITERATION instead of raising StopIteration
+            return MP_OBJ_STOP_ITERATION;
         } else {
             // re-raise exception
             nlr_raise(nlr.ret_val);