redline.append_history fails on macOS

[DNSGeek]

The built in libreadline on macOS does not have append_history, causing the writing of the history file to fail on exit. I tried to submit a PR but did not have permission. Here is my change:

line 373

              # Check for missing append_history. Will fail on macOS
              if "append_history" not in dir(readline):
                  readline.write_history_file(config.HISTFILE)
                  return