py: bytes(): Make sure we add values as bytes, not as chars.
diff --git a/py/objstr.c b/py/objstr.c
index 5cd0f28..3b2ce8f 100644
--- a/py/objstr.c
+++ b/py/objstr.c
@@ -223,7 +223,7 @@
     mp_obj_t iterable = mp_getiter(args[0]);
     mp_obj_t item;
     while ((item = mp_iternext(iterable)) != MP_OBJ_STOP_ITERATION) {
-        vstr_add_char(&vstr, MP_OBJ_SMALL_INT_VALUE(item));
+        vstr_add_byte(&vstr, MP_OBJ_SMALL_INT_VALUE(item));
     }
 
     return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);