Typical exception class. Use it like this:
throw new WikiaException("Something bad happened");
One thing to note, there is a report() function in the WikiaException that logs uncaught exceptions to the normal error log. At the moment, we do not display a visible error page. There is just a blank a page with a GA tracking cookie on it. If we want to add an error page at some future date, we can add it to the WikiaException::report() function.