Locked_tables_list::reopen_tables() is used under LOCK TABLES to reopen all tables that were closed. The failure to reopen might fail the whole statement.
This is wrong, because reopen might fail for reason completely unrelated to the current statement, because of something that happened earlier. Test case:
this works. But if one uncomments drop table, repair will fail — because reopen_tables tries to reopen all closed tables, so it'll try to reopen t1, which no longer exists.
That's why in some cases the return value of Locked_tables_list::reopen_tables() is ignored (which doesn't help, as it still sets the error status in the thd), and sometimes it is followed by the thd->clear_error() (which is too indiscriminate, and still leaves a warning).
Ideally, Locked_tables_list::reopen_tables() will take a table as an argument and will reopen just that one table.