HTTP Error 400: Bad Request when trying

[Mikeltxo15]

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• You will be asked some questions and requested to provide some information, please read them carefully and answer honestly
• Put an x into all the boxes [ ] relevant to your issue (like this: [x])
• Use the Preview tab to see what your issue will actually look like

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Make sure you are using the latest version: run youtube-dl --version and ensure your version is 2019.04.17. If it's not, read this FAQ entry and update. Issues with outdated version will be rejected.

• [ X ] I've verified and I assure that I'm running youtube-dl 2019.04.17

Before submitting an issue make sure you have:

• [ X ] At least skimmed through the README, most notably the FAQ and BUGS sections
• [ X ] Searched the bugtracker for similar issues including closed ones
• [ X ] Checked that provided video/audio/playlist URLs (if any) are alive and playable in a browser

What is the purpose of your issue?

• [ X ] Bug report (encountered problems with youtube-dl)
• Site support request (request for adding support for a new site)
• Feature request (request for a new functionality)
• Question
• Other

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The following sections concretize particular purposed issues, you can erase any section (the contents between triple ---) not applicable to your issue

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If the purpose of this issue is a bug report, site support request or you are not completely sure provide the full verbose output as follows:

Add the -v flag to your command line you run youtube-dl with (youtube-dl -v <your command line>), copy the whole output and insert it here. It should look similar to one below (replace it with your log inserted between triple ```):

[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['-v', '--call-home', '-i', '--download-archive', '/home/%user%/Youtube/Archive', '-o', '~/Youtube/%(upload_date)s-%(title)s-%(uploader)s.%(ext)s', '-u', 'PRIVATE', '-p', 'PRIVATE', '-f', 'bestvideo[height<481]+bestaudio', 'https://www.youtube.com/playlist?list=WL']
[debug] Encodings: locale UTF-8, fs utf-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2019.04.17
[debug] Python version 3.7.3 (CPython) - Linux-5.0.8-arch1-1-ARCH-x86_64-with-arch
[debug] exe versions: ffmpeg 4.1.3, ffprobe 4.1.3, rtmpdump 2.4
[debug] Proxy map: {}
[debug] Public IP address: 190.183.34.193
[youtube:watchlater] Downloading login page
[youtube:watchlater] Looking up account info
[youtube:watchlater] Logging in
WARNING: Unable to log in: HTTP Error 400: Bad Request
[youtube:watchlater] WL: Downloading webpage
ERROR: This playlist does not exist.
Traceback (most recent call last):
  File "/usr/lib/python3.7/site-packages/youtube_dl/YoutubeDL.py", line 796, in extract_info
    ie_result = ie.extract(url)
  File "/usr/lib/python3.7/site-packages/youtube_dl/extractor/common.py", line 529, in extract
    ie_result = self._real_extract(url)
  File "/usr/lib/python3.7/site-packages/youtube_dl/extractor/youtube.py", line 2927, in _real_extract
    _, playlist = self._extract_playlist('WL')
  File "/usr/lib/python3.7/site-packages/youtube_dl/extractor/youtube.py", line 2439, in _extract_playlist
    raise ExtractorError(message, expected=True)
youtube_dl.utils.ExtractorError: This playlist does not exist.

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Description of your issue, suggested solution and other information

Explanation of your issue in arbitrary form goes here. Please make sure the description is worded well enough to be understood. Provide as much context and examples as possible.
If work on your issue requires account credentials please provide them or explain how one can obtain them.

Hello, I´ve been using youtube-dl for some months now, through the use of a script I wrote. What it does is log in to youtube with my credentials and download the Watch Later playlist, to which I previously add the videos I want to see. In this way, I don't need to manually input the individual URL of all the videos I want to see. However, two weeks ago, the script stopped working. When I run the command on it's own, it exits with a HTTP Error 400: Bad Request saying it couldn't log in to my account, therefore it couldn't find the playlist either.
The problem seems similar to the one present in Bug Report #2975, but in that case it could log into the account but failed in detecting the videos, while in this case it fails to log in. That's why i opened a different Issue.
My guess is Youtube probably changed something about the way to login, which is causing this error.
Many thanks, I'm sorry i can't give more info, and good luck. Also, thanks for all the work needed to create and mantain this program, it's really helpful.

[dstftw]

Duplicate of #11270.