youtube video not downloading

[STM101]

I also tried:
youtube-dl-casept -v -x --audio-format mp3 https://www.youtube.com/watch?v=mlz4O6KRHMA

youtube-dl-casept -v https://www.youtube.com/watch?v=mlz4O6KRHMA
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['-v', 'https://www.youtube.com/watch?v=mlz4O6KRHMA']
[debug] Encodings: locale UTF-8, fs utf-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2019.05.11
[debug] Python version 3.6.7 (CPython) - Linux-4.15.0-72-generic-i686-athlon-with-Ubuntu-16.04-xenial
[debug] exe versions: ffmpeg 4.1, ffprobe 4.1
[debug] Proxy map: {}
[youtube] mlz4O6KRHMA: Downloading webpage
[youtube] mlz4O6KRHMA: Downloading video info webpage
WARNING: Unable to extract video title
[youtube] {18} signature length 109, html5 player vfl7Ksmll
[youtube] mlz4O6KRHMA: Downloading player https://www.youtube.com/yts/jsbin/player_ias-vfl7Ksmll/en_US/base.js
ERROR: Signature extraction failed: Traceback (most recent call last):
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/youtube.py", line 1342, in _decrypt_signature
video_id, player_url, s
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/youtube.py", line 1250, in _extract_signature_function
res = self._parse_sig_js(code)
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/youtube.py", line 1314, in _parse_sig_js
jscode, 'Initial JS player signature function name', group='sig')
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/common.py", line 1004, in _search_regex
raise RegexNotFoundError('Unable to extract %s' % _name)
youtube_dl.utils.RegexNotFoundError: Unable to extract Initial JS player signature function name; 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.
(caused by RegexNotFoundError('Unable to extract \x1b[0;34mInitial JS player signature function name\x1b[0m; 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.',)); 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.
Traceback (most recent call last):
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/youtube.py", line 1342, in _decrypt_signature
video_id, player_url, s
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/youtube.py", line 1250, in _extract_signature_function
res = self._parse_sig_js(code)
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/youtube.py", line 1314, in _parse_sig_js
jscode, 'Initial JS player signature function name', group='sig')
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/common.py", line 1004, in _search_regex
raise RegexNotFoundError('Unable to extract %s' % _name)
youtube_dl.utils.RegexNotFoundError: Unable to extract Initial JS player signature function name; 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.
Traceback (most recent call last):
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/youtube.py", line 1342, in _decrypt_signature
video_id, player_url, s
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/youtube.py", line 1250, in _extract_signature_function
res = self._parse_sig_js(code)
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/youtube.py", line 1314, in _parse_sig_js
jscode, 'Initial JS player signature function name', group='sig')
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/common.py", line 1004, in _search_regex
raise RegexNotFoundError('Unable to extract %s' % _name)
youtube_dl.utils.RegexNotFoundError: Unable to extract Initial JS player signature function name; 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.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/YoutubeDL.py", line 796, in extract_info
ie_result = ie.extract(url)
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/common.py", line 529, in extract
ie_result = self._real_extract(url)
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/youtube.py", line 1989, in _real_extract
encrypted_sig, video_id, player_url, age_gate)
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/youtube.py", line 1352, in _decrypt_signature
'Signature extraction failed: ' + tb, cause=e)
youtube_dl.utils.ExtractorError: Signature extraction failed: Traceback (most recent call last):
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/youtube.py", line 1342, in _decrypt_signature
video_id, player_url, s
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/youtube.py", line 1250, in _extract_signature_function
res = self._parse_sig_js(code)
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/youtube.py", line 1314, in _parse_sig_js
jscode, 'Initial JS player signature function name', group='sig')
File "/snap/youtube-dl-casept/148/lib/python3.6/site-packages/youtube_dl/extractor/common.py", line 1004, in _search_regex
raise RegexNotFoundError('Unable to extract %s' % _name)
youtube_dl.utils.RegexNotFoundError: Unable to extract Initial JS player signature function name; 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.
(caused by RegexNotFoundError('Unable to extract \x1b[0;34mInitial JS player signature function name\x1b[0m; 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.',)); 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.