Trying to set up a site-wide File System repository on a Moodle 2.8.12 site.
The error means that a new admin page 'foo' (the one you're developing right now) is not registered with the Admin menu. It is triggered with the call:
The solution is to add a reference to the page in the appropriate file in admin/settings/XXX.php. Something like:
$ADMIN->add("parent_section", new admin_externalpage('foo', "Foo Admin Component", "$CFG->wwwroot/$CFG->admin/foo.php"));
Could someone put that into plain English please e.g. what file is XXX.php supposed to be referring to, what would the new admin page be called and do I really need to manually add code for something that is supposed to be core functionality? Something doesn't seem to be quite right with this "solution".
There's no errors with full debugging on and I can add a course repository OK.