Add dirty support for macos; retry iperf3 on error; alert with sounds

[maximweb]

I've been looking for something like this package for ages! Very nice work.

Unfortunately, I run MacOS, so I created a quick-and-dirty version for Mac. It is rather a proof of concept rather than a full pull request, but I thought I might still share it for some ideas. Not sure, whether I find the time to clean it up any time soon.

I did not find iw for Mac, so I used a combination of ifconfig and airport commands to get the necessary information.

Some features may be interesting for any OS, though:

• Occasionally, iperf3 exited with an error. So a couple of retries would be nice, before crashing the program when the results cannot be added. (In lack of a "sum..." key in the resulting dict).
• A notification sound, alerting the user when a benchmark is completed or was aborted is very helpful, especially for multiple iterations. For Mac, I used text to speech feature os.system("say 'Benchmark completed'")

A thing I did not implement, but would also be nice:

• Optionally add the measurement results as number next to the respective points on the map.

[6xthFNGR]

I support the iperf3 comment: Sometimes the entire benchmark crashes and the GUI closes, loosing some result, just because an iperf connection dropped.
Inputting more forgiving commands for repeating and reestablishing connection would help,
as well as decoupling it from further crashes and exiting the GUI instead of just showing a timeout error message.