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] 6Wgw_wT0_GY: nsig extraction failed: Some formats may be missing
         n = 7s8Cmgs_loj6Eumoa ; 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] 6Wgw_wT0_GY: nsig extraction failed: Some formats may be missing
         n = i4ZVpGygQMeuwWNBe ; player = https://www.youtube.com/s/player/e7567ecf/player_ias.vflset/en_US/base.js