viki does not log in

[allanf181]

Checklist

• I'm reporting a broken site support
• I've verified that I'm running youtube-dl version 2020.05.08
• 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 issues including closed ones

Verbose log

[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['https://www.viki.com/tv/31706c-guardian-the-lonely-and-great-god', '-s', '-F', '-u', 'PRIVATE', '-p', 'PRIVATE', '--verbose']
[debug] Encodings: locale UTF-8, fs utf-8, out utf-8, pref UTF-8
[debug] youtube-dl version 2020.05.08
[debug] Python version 3.8.2 (CPython) - Linux-4.4.0-18362-Microsoft-x86_64-with-glibc2.29
[debug] exe versions: none
[debug] Proxy map: {}
[viki:channel] Logging in
ERROR: Unable to download JSON metadata: HTTP Error 404: Not Found (caused by <HTTPError 404: 'Not Found'>); please report this issue on https://yt-dl.org/bug . Make sure you are using the latest version; see  https://yt-dl.org/update  on how to update. Be sure to call youtube-dl with the --verbose flag and include its complete output.
  File "/home/user/.local/lib/python3.8/site-packages/youtube_dl/extractor/common.py", line 627, in _request_webpage
    return self._downloader.urlopen(url_or_request)
  File "/home/user/.local/lib/python3.8/site-packages/youtube_dl/YoutubeDL.py", line 2238, in urlopen
    return self._opener.open(req, timeout=self._socket_timeout)
  File "/usr/lib/python3.8/urllib/request.py", line 531, in open
    response = meth(req, response)
  File "/usr/lib/python3.8/urllib/request.py", line 640, in http_response
    response = self.parent.error(
  File "/usr/lib/python3.8/urllib/request.py", line 569, in error
    return self._call_chain(*args)
  File "/usr/lib/python3.8/urllib/request.py", line 502, in _call_chain
    result = func(*args)
  File "/usr/lib/python3.8/urllib/request.py", line 649, in http_error_default
    raise HTTPError(req.full_url, code, msg, hdrs, fp)

Description

Api sites return 404

[tarhan]

It only returns 404 status for sessions.json endpoint both for v4 and v5 APIs.
That is because viki.py do not send mandatory x-viki-app-ver and x-viki-as-id HTTP headers during logging in.