PHP Warning during installation

I installed Koko analytics on my local site, just to make sure everything works as expected before installing on my live site. I received numerous warnings:

No such file or directory in /Users/xxxxx/Sites/wordpress/wp-content/plugins/koko-analytics/migrations/1.0.21-unlink-custom-endpoint-and-update-option.php on line 6

Warning: Cannot modify header information - headers already sent by (output started at /Users/xxxxx/Sites/wordpress/wp-content/plugins/koko-analytics/migrations/1.0.21-unlink-custom-endpoint-and-update-option.php:6) in /Users/petermetz/Sites/wordpress/wp-includes/functions.php on line 6274

Warning: Cannot modify header information - headers already sent by (output started at /Users/xxxxx/Sites/wordpress/wp-content/plugins/koko-analytics/migrations/1.0.21-unlink-custom-endpoint-and-update-option.php:6) in /Users/petermetz/Sites/wordpress/wp-admin/includes/misc.php on line 1310

Warning: Cannot modify header information - headers already sent by (output started at /Users/xxxxx/Sites/wordpress/wp-content/plugins/koko-analytics/migrations/1.0.21-unlink-custom-endpoint-and-update-option.php:6) in /Users/petermetz/Sites/wordpress/wp-admin/admin-header.php on line 9

Any ideas why this might be?

Thanks