This just struck me as so "cute" that I had to share.
# Usage:
···
#
# if find_bug then
# bug! "unknown bug found"
# end
#
class ScriptBug < Exception; end
def bug!( message = 'must not happen' )
raise ScriptBug, "\n[SCRIPT BUG] " + message
end
Lovely, Minero Aoki! 
T.