New is implied by raise, 2nd is the message.

lib/jekyll/converters/markdown.rb

@@ -20,7 +20,7 @@ module Jekyll
           else
             $stderr.puts "Invalid Markdown processor: #{@config['markdown']}"
             $stderr.puts "  Valid options are [ maruku | rdiscount | kramdown | redcarpet ]"
-            raise FatalException.new("Invalid Markdown process: #{@config['markdown']}")
+            raise FatalException, "Invalid Markdown process: #{@config['markdown']}"
         end
         @setup = true
       end