When using youtube-dl from another python script with the quiet option
on, and a post procesor for extract the audio. The message of deleting
video shows in the first script logs (as it goes to stderr).
There is no way to keep this quiet as it's treated as an error, even if,
for me, it's not.
Improved option '--srt-lang'
- it shows the argument in case of missing subtitles
- added language suffix for non-english languages (e.g. video.it.srt)
With Python 3, the titlebar wouldn't get updated for a long time (due to
stderr buffering), and when it did, the title would be shown as b'...'
representation.