running the testsuite on community-mysql-server-5.7.17-1.fc25.x86_64 fails with:

rpl.rpl_semi_sync_event 'mix'            [ fail ]
        Test ended at 2017-01-30 16:30:59

CURRENT_TEST: rpl.rpl_semi_sync_event
mysqltest: At line 103: query 'UNINSTALL PLUGIN rpl_semi_sync_master' failed: 1883: Plugin 'rpl_semi_sync_master' cannot be uninstalled now. Stop any active semisynchronous slaves of this master first.

The result from queries just before the failure was:
< snip >
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 17;
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 16;
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 15;
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 14;
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 13;
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 12;
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 11;
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 10;
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 9;
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 8;
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 7;
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 6;
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 5;
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 4;
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 3;
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 2;
UPDATE t1 SET f = CONCAT('up_',CONNECTION_ID()) WHERE i = 1;
SET GLOBAL event_scheduler = OFF;
include/stop_slave.inc
UNINSTALL PLUGIN rpl_semi_sync_slave;
safe_process[15802]: Child process: 15803, exit: 1

 - the logfile can be found in '/var/tmp/testELX/log/rpl.rpl_semi_sync_event-mix/rpl_semi_sync_event.log'