addFeUserToNotify leads to faulty require_once
when setting addFeUserToNotify to 1 (send mail to FE user who created the event) cal is quitting with
Core: Error handler (FE): PHP Warning: require_once(/var/www/[path]/typo3conf/ext/cal/cron/class.tx_cal_reminder_scheduler.php): failed to open stream: No such file or directory in /[path]/typo3_src-6.2.14/typo3/sysext/core/Classes/Utility/GeneralUtility.php line 4738
which is quite funny, as this seems to be an old function call inside (?) cal. The directory cal/cron/ simply does not exists any more...
When unsetting the addFeUserToNotify-Option, everything is fine, event gets created but no mail is sent.