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 = M2fE9yVMuH9P-1c1B ; 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 = cDU3Nz9RKkBZ4gRcT ; player = https://www.youtube.com/s/player/e7567ecf/player_ias.vflset/en_US/base.js