Gives warning to set LC_ALL even though it is already set

[Germs2004]

Checklist

• I'm reporting a broken site support issue
• I've verified that I'm running youtube-dl version 2020.07.28
• I've checked that all provided URLs are alive and playable in a browser
• I've checked that all URLs and arguments with special characters are properly quoted or escaped
• I've searched the bugtracker for similar bug reports including closed ones
• I've read bugs section in FAQ

Verbose log

$ ./youtube-dl -v 'https://www.youtube.com/watch?v=C0DPdy98e4c'
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'-v', u'https://www.youtube.com/watch?v=C0DPdy98e4c']
WARNING: Assuming --restrict-filenames since file system encoding cannot encode all characters. Set the LC_ALL environment variable to fix this.
[debug] Encodings: locale ANSI_X3.4-1968, fs ANSI_X3.4-1968, out ANSI_X3.4-1968, pref ANSI_X3.4-1968
[debug] youtube-dl version 2020.07.28
[debug] Python version 2.7.16 (CPython) - Linux-5.4.0-42-generic-x86_64-with-debian-10.4
[debug] exe versions: none
[debug] Proxy map: {}
[youtube] C0DPdy98e4c: Downloading webpage
[debug] Default format spec: best/bestvideo+bestaudio
[debug] Invoking downloader on u'https://r2---sn-hp57yn7r.googlevideo.com/videoplayback?expire=1596415883&ei=KwsnX_a2F8rJ4QTlpqsY&ip=47.195.19.170&id=o-ALlYMY189_un8gYd4_zFHLa3mIdWbQsuiF4u0z7TFkLy&itag=18&source=youtube&requiressl=yes&mh=m8&mm=31%2C29&mn=sn-hp57yn7r%2Csn-hp57kn7l&ms=au%2Crdu&mv=m&mvi=2&pl=16&initcwndbps=1402500&vprv=1&mime=video%2Fmp4&gir=yes&clen=552999&ratebypass=yes&dur=17.600&lmt=1407413068816851&mt=1596394226&fvip=2&fexp=23883098&c=WEB&sparams=expire%2Cei%2Cip%2Cid%2Citag%2Csource%2Crequiressl%2Cvprv%2Cmime%2Cgir%2Cclen%2Cratebypass%2Cdur%2Clmt&sig=AOq0QJ8wRQIgUil3D0m0HejCvuO2G3KhgdsOFoeARrNS_t9sf0AhgpACIQDz9qm4F2po6yom_I_9SKhvE2RwWswACbbV4sAIRLaB4A%3D%3D&lsparams=mh%2Cmm%2Cmn%2Cms%2Cmv%2Cmvi%2Cpl%2Cinitcwndbps&lsig=AG3C_xAwRQIgJLwtnHe-6LinBZOLHswfD1VWGosRoZ5J-SbiRKwnp-ECIQD72rdQYaPMOLA5ondJGEI0TPwuNRGgnIz-V_bsXnMVmQ%3D%3D'
[download] TEST_VIDEO-C0DPdy98e4c.mp4 has already been downloaded
[download] 100% of 540.04KiB

Description

When I run youtube-dl, it gives a warning and says I can set LC_ALL to prevent the warning. I set that variable but I still get that warning. It seems like youtube-dl is failing to detect that the LC_ALL variable has been set or else its warning message is wrong.

I am running youtube-dl in a Docker container that runs image "mcr.microsoft.com/dotnet/core/sdk:3.1". I set the environment variable in the docker-compose.yml file like this:

environment:
          - TZ=America/New_York
          - LANG=en_US.UTF-8
          - LANGUAGE=en_US.UTF-8
          - LC_ALL=en_US.UTF-8

I verified that the container does see that the variable has been set. printenv LC_ALL shows LC_ALL=en_US.UTF-8.

See the screenshot above to make things more clear.