test if the find_select_handler is actually working

    (expecially for the partition engine)
       Seems it implemented for the federatedex egngine only.

sql/sql_select.cc

@@ -5133,6 +5133,7 @@ select_handler *find_select_handler_inner(THD *thd,
     handlerton *ht= tbl->table->file->partition_ht();
     if (!ht->create_select)
       continue;
+    DBUG_ASSERT(0);
     select_handler *sh= ht->create_select(thd, select_lex, select_lex_unit);
     if (sh)
       return sh;