rpl.rpl_slow_query_log failed in buildbot

rpl.rpl_slow_query_log 'stmt'            w1 [ fail ]

        Test ended at 2017-06-16 17:34:23

CURRENT_TEST: rpl.rpl_slow_query_log

mysqltest: At line 293: "Assertion failed! Master and slave slow log contents differ. Bailing out!"

The result from queries just before the failure was:

< snip >

**** Now do inserts again, but first add an index to the table.

**** Outcome: Note that the slave contains the same one entry (as 

****          the master does)  whereas before the patch it did not.

********************************************************************

ALTER TABLE t1 ADD INDEX id1(a);

INSERT INTO t1 values(1, sleep(3));

connection slave;

connection master;

***********************************************

** DUMPING MASTER SLOW LOG CONTENTS 

***********************************************

SELECT * FROM mysql.slow_log;

start_time	user_host	query_time	lock_time	rows_sent	rows_examined	db	last_insert_id	insert_id	server_id	sql_text	thread_id	rows_affected

connection slave;

***********************************************

** DUMPING SLAVE SLOW LOG CONTENTS 

***********************************************

SELECT * FROM mysql.slow_log;

start_time	user_host	query_time	lock_time	rows_sent	rows_examined	db	last_insert_id	insert_id	server_id	sql_text	thread_id	rows_affected

2017-06-16 17:34:20.000568	[SQL_SLAVE] @  []	00:00:03.000568	00:00:00.000304	0	0	test	0	0	2	INSERT INTO t1 values(1, sleep(3))	25	1

More results from queries before failure can be found in /usr/local/mariadb-10.2.7-linux-x86_64/mysql-test/var/1/log/rpl_slow_query_log.log

 - skipping '/usr/local/mariadb-10.2.7-linux-x86_64/mysql-test/var/1/log/rpl.rpl_slow_query_log-stmt/'