Events Calendar 3.6 // Add 'nofollow' attribute to Event Website URL

gistfile1.php

add_filter( 'tribe_get_event_website_link', 'add_no_follow_event_website', 10, 2);

function add_no_follow_event_website( $html ) {
	//Strip out HTML
	$url = strip_tags( $html );

	//Add nofollow attribute
	return sprintf( '<a href="%1$s" rel="nofollow" target="_self">%1$s</a>', $url );
}