/usr/lib/mysql-testsuite/r/handler_socket.result is in percona-server-test-5.6 5.6.22-rel71.0-0ubuntu4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | call mtr.add_suppression("handlersocket: open_files_limit is too small");
INSTALL PLUGIN handlersocket SONAME 'HANDLER_SOCKET';
Restarting mysqld for bug 1397859 test...
UNINSTALL PLUGIN handlersocket;
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