When trying to view the participants page for a course that has both:
a) a 'Random glossary entry' block; and
b) at least one entry in that block;
Trying to view the 'course participants' page fails.
Expected Output: Participants page displays.
Actual Output: "Fatal error: Call to undefined function file_rewrite_pluginfile_urls() in /var/www/html/moodle20/blocks/glossary_random/block_glossary_random.php on line 95" (or a blank page if debugging is off).
Seems all thats needed is to require the filelib.php at the start of the function.