rocksdb.allow_no_primary_key failed in buildbot, server crashed

rocksdb.allow_no_primary_key             w3 [ fail ]  Found warnings/errors in server log file!

        Test ended at 2018-05-24 23:46:42

line

Attempting backtrace. You can use the following information to find out

^ Found warnings in /dev/shm/var/3/log/mysqld.1.err

ok

 - found 'core.7289' (0/0)

Trying 'dbx' to get a backtrace

gdb not found, cannot get the stack trace