main.ctype_binary failed in buildbot with 1406: Data too long for column

main.ctype_binary                        w1 [ fail ]

        Test ended at 2020-09-25 14:03:37

CURRENT_TEST: main.ctype_binary

mysqltest: In included file "./include/ctype_numconv.inc": 

included from /usr/share/mysql/mysql-test/main/ctype_binary.test at line 9:

At line 216: query 'create table t1 as select concat(rand()) as c1' failed: 1406: Data too long for column 'c1' at row 1

The result from queries just before the failure was:

< snip >

hex(concat(round(0.5)))

31

create table t1 as select concat(round(0.5)) as c1;

show create table t1;

Table	Create Table

t1	CREATE TABLE `t1` (

  `c1` varbinary(3) DEFAULT NULL

) ENGINE=MyISAM DEFAULT CHARSET=latin1

drop table t1;

select hex(concat(sign(0.5)));

hex(concat(sign(0.5)))

31

create table t1 as select concat(sign(0.5)) as c1;

show create table t1;

Table	Create Table

t1	CREATE TABLE `t1` (

  `c1` varbinary(2) DEFAULT NULL

) ENGINE=MyISAM DEFAULT CHARSET=latin1

drop table t1;

create table t1 as select concat(rand()) as c1;