py: bytes(): Make sure we add values as bytes, not as chars.

py/objstr.c

@@ -223,7 +223,7 @@ STATIC mp_obj_t bytes_make_new(mp_obj_t type_in, mp_uint_t n_args, mp_uint_t n_k
     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);