Merge pull request #990 from sjml/patch-1

Generate can fail if Pygments can't parse a code block

plugins/pygments_code.rb

@@ -21,7 +21,11 @@ module HighlightCode
       if File.exist?(path)
         highlighted_code = File.read(path)
       else
+        begin
           highlighted_code = Pygments.highlight(code, :lexer => lang, :formatter => 'html', :options => {:encoding => 'utf-8'})
+        rescue MentosError
+          raise "Pygments can't parse unknown language: #{lang}."
+        end
         File.open(path, 'w') {|f| f.print(highlighted_code) }
       end
     else