FFMPEG bug causes Obico not to respect RFC2396 for stream URLs causing compatible mode to run at 0.1fps

[puterboy]

In Octoprint settings, under "Webcam & Timelapse", I set stream url to:
http ://myrpi:8080?action=stream which is a valid RFC2396 URL.

However, ffmpeg fails to recognize the URL and returns:
http://myrpi:8080?action=stream: Server returned 400 Bad Request

See the bug report: https://trac.ffmpeg.org/ticket/8466

Obico doesn't detect this bug and merrily launches ffmpeg with the faulty URL.
ffmpeg fails (silently) and then Obico defaults to 0.1fps snapshots.

Suggested fix is either:

1. Warn users if malformed URL
2. Or fix stream_url in webcam_stream.py to insert a slash if missing before '?'

[puterboy]

Of course, until ffmpeg or Obico code is adjusted, users can avoid the problem by making sure there is a "/" before the '?'.
i.e., change http://myrpi:8080?action=stream to http://myrpi:8080/?action=stream

[puterboy]

Moved to TheSpaghettiDetective/OctoPrint-TheSpaghettiDetective#1