bug#43418: ffprobe/avprobe and ffmpeg/avconv should be added as dependencies of youtube-dl so it will function correctly

[Nathan Dehnel]

bash-5.0$ youtube-dl -x https://www.youtube.com/watch?v=7Ijd_iN9Blk
[youtube] 7Ijd_iN9Blk: Downloading webpage
[download] Deadmau5 - Hit Save-7Ijd_iN9Blk.webm has already been downloaded
[download] 100% of 15.45MiB
ERROR: ffprobe/avprobe and ffmpeg/avconv not found. Please install one.