docs: def print_no_files_found(opts):
      """
      Prints message that no files were found in the input directory with the
      given list of extensions.
  
      :param opts: Namespace object created from command-line arguments. Must
      have the attributes 'extensions' and 'input'
      """
      msg =  "No files found with [" +', '.join(opts.extensions) + "] "
      msg += "extension" +("s " if len(opts.extensions) > 1 else " ")
      msg += "in " + opts.input
      # if recursive
      msg += " or any of its subdirectories"
      print(msg)