try_call
When the manifest is not downloadable by native downloader, it already is able to detect it and switch to `ffmpeg`. So there doesn't seem to be a reason anymore to use ffmpeg as the preferred downloader
closes #223 Authored by: nao20010128nao Modified from: 9e4a0e061a/youtube_dl/extractor/whowatch.py
9e4a0e061a/youtube_dl/extractor/whowatch.py