CodeBlock: (block) ->
  { label } = block.classes
  fname, errfname = os.tmpname!, os.tmpname!
  cmd = "pygmentize -f html -O style=dracula,wrapcode,classprefix=py- -l %s %s 2>%s"

  with io.open fname, "w"
    \write block.text
    \close!

  lexer = switch label
    when "moon", "moonscript"
      cmd = cmd .. " -x"
      "moonscript.py"
    else
      label or "text"

  f = io.popen cmd\format lexer, fname, errfname

  out = with f\read"*a"
    f\close!

  if out == ""
    e = io.open errfname, "r"

    err = with e\read"*a"
      e\close!

    assert err\match("Error: no lexer for alias '#{label}' found"),
      "Failed to parse pygmentize result, is pygments installed?"

    block
  else
    pandoc.RawBlock "html", out