Overriding the suspension page in WPMU

WPMU uses the function  to output suspension, deletion, spam, etc. notices. These notices are very boring in appearance and offer no links to the main WPMU install, no explanation, nothing - just a nondescript error.

There is a  filter (by the same name) that is intended to be used on the message itself, but as this filter executes before the   function is called, we can write a plugin that outputs a custom error page of our choosing, then calls   or   to prevent the default page from ever showing up.

Code
This goes in WPMU's  folder.