innodb.truncate_foreign failed in buildbot with wrong error code

innodb.truncate_foreign 'innodb'         w2 [ fail ]

        Test ended at 2020-05-06 18:44:48

CURRENT_TEST: innodb.truncate_foreign

mysqltest: At line 41: query 'TRUNCATE TABLE child' succeeded - should have failed with errno 1205...

The result from queries just before the failure was:

< snip >

a

2

connect  dml,localhost,root;

SET DEBUG_SYNC='foreign_constraint_update_cascade SIGNAL fk WAIT_FOR go';

UPDATE parent SET a=3;

connection default;

SET DEBUG_SYNC='now WAIT_FOR fk';

SET lock_wait_timeout=1;

TRUNCATE TABLE child;

ERROR HY000: Lock wait timeout exceeded; try restarting transaction

SET DEBUG_SYNC='now SIGNAL go';

connection dml;

SELECT * FROM child;

a

3

SET DEBUG_SYNC='foreign_constraint_check_for_update SIGNAL fk WAIT_FOR go';

DELETE FROM parent;

connection default;

SET DEBUG_SYNC='now WAIT_FOR fk';

TRUNCATE TABLE child;