WARNING: [youtube] Falling back to generic n function search
         player = https://www.youtube.com/s/player/e7567ecf/player_ias.vflset/en_US/base.js
WARNING: [youtube] 4t-Ukd6UhXs: nsig extraction failed: Some formats may be missing
         n = dqw0U-x2vIXWHBi1i ; player = https://www.youtube.com/s/player/e7567ecf/player_ias.vflset/en_US/base.js
WARNING: [youtube] Falling back to generic n function search
         player = https://www.youtube.com/s/player/e7567ecf/player_ias.vflset/en_US/base.js
WARNING: [youtube] 4t-Ukd6UhXs: nsig extraction failed: Some formats may be missing
         n = ajhZ_hPlIcTlY33IP ; player = https://www.youtube.com/s/player/e7567ecf/player_ias.vflset/en_US/base.js