This used to be bug http://bugs.mysql.com/bug.php?id=55983 in MySQL
While running in MTR-1 mode, MTR produces bootsrap SQL file starting with
"use mysql-- Copyright ..."
(no semicolon and line break after 'use mysql')
While earlier the syntax was accepted and handled, with the new implementation of server bootstrap it is not anymore, which makes server startup fail.
It might be a problem for those who uses runall.pl RQG script (unlike runall-new.pl, it still uses MTR1 to start server)
How to repeat:
Fix (for 10.0-serg revno 3452):