miles@miles-T410:~$ youtube-dl -f 140 https://www.youtube.com/watch?v=GpkewaEgtVk
[youtube] GpkewaEgtVk: Downloading webpage
[youtube] GpkewaEgtVk: Downloading video info webpage
[youtube] GpkewaEgtVk: Extracting video information
[youtube] GpkewaEgtVk: Downloading js player en_US-vflnrstgx
ERROR: Signature extraction failed: Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/youtube_dl/extractor/youtube.py", line 877, in _decrypt_signature
    video_id, player_url, s
  File "/usr/lib/python2.7/dist-packages/youtube_dl/extractor/youtube.py", line 792, in _extract_signature_function
    res = self._parse_sig_js(code)
  File "/usr/lib/python2.7/dist-packages/youtube_dl/extractor/youtube.py", line 855, in _parse_sig_js
    initial_function = jsi.extract_function(funcname)
  File "/usr/lib/python2.7/dist-packages/youtube_dl/jsinterp.py", line 241, in extract_function
    raise ExtractorError('Could not find JS function %r' % funcname)
ExtractorError: Could not find JS function u'gr'; 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 ExtractorError(u"Could not find JS function u'gr'; 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.