So... how do you have a file from an older version of Moodle?
If you are *really* running a clean copy of Moodle 3.6 then you can't have /home/prom/public_html/moodle30/lib/eventslib.php.
See https://github.com/moodle/moodle/tree/MOODLE_36_STABLE/lib for the correct contents of lib/
That file was deleted between versions 3.5 and 3.6 (it's in 3.5 but not 3.6)
My guess is that you are using an old plugin that needed this now deprecated library file. To fix the plugin dependency you have copied the file from the older version. Just a guess