docs: def check_for_wkhtmltohtml():
      """
      Checks to see if the wkhtmltohtml binary is installed. Raises error if not.
      """
      locator = 'where' if sys.platform == 'win32' else 'which'
  
      wkhtmltopdf = (subprocess.Popen([locator, 'wkhtmltopdf'],
                                      stdout=subprocess.PIPE)
                     .communicate()[0].strip())
  
      if not os.path.exists(wkhtmltopdf):
          logging.error(
              'No wkhtmltopdf executable found. Please install '
              'wkhtmltopdf before trying again - {}'.format(WKHTMLTOPDF_URL))
          raise ValueError(
              'No wkhtmltopdf executable found. Please install '
              'wkhtmltopdf before trying again - {}'.format(WKHTMLTOPDF_URL))