YouTube error: "extraction failed: Some formats may be missing"


```
WARNING: [youtube] … : nsig extraction failed: Some formats may be missing
         Install PhantomJS to workaround the issue. Please download it from https://phantomjs.org/download.html
         n = sEzgUcjD-HQIyqiTcl ; player = https://www.youtube.com/s/player/20830619/player_ias.vflset/en_US/base.js
```

