mariabackup.unencrypted_page_compressed failed in buildbot with wrong error

mariabackup.unencrypted_page_compressed  w3 [ fail ]

        Test ended at 2019-01-14 08:38:28

CURRENT_TEST: mariabackup.unencrypted_page_compressed

mysqltest: At line 41: command "$XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf --backup --target-dir=$targetdir > $backuplog" failed with wrong error: 255

The result from queries just before the failure was:

call mtr.add_suppression("InnoDB: Table `test`.`t1` has an unreadable root page");

SET GLOBAL innodb_purge_rseg_truncate_frequency = 1;

CREATE TABLE t1 (a INT AUTO_INCREMENT PRIMARY KEY, b TEXT, c char(200)) ENGINE=InnoDB page_compressed=yes;

insert into t1(b, c) values("mariadb", "mariabackup");

InnoDB		0 transactions not purged

# Corrupt the table

# xtrabackup backup