Error while using an HTTP proxy server without HTTP/1.0 support

[lamg]

• I've verified that I'm running youtube-dl version 2019.09.28
• 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://youtu.be/nmoMGP3zn_k
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'-v', u'https://youtu.be/nmoMGP3zn_k']
[debug] Encodings: locale UTF-8, fs UTF-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2019.09.28
[debug] Python version 2.7.15+ (CPython) - Linux-4.15.0-58-generic-x86_64-with-LinuxMint-19-tara
[debug] exe versions: ffmpeg 3.4.6, ffprobe 3.4.6
[debug] Proxy map: {'http': 'http://10.2.4.70:8081/', 'https': 'http://10.2.4.70:8081/', 'no': 'localhost,127.0.0.0/8,::1,*.upr.edu.cu,10.2.0.0/16'}
[youtube] nmoMGP3zn_k: Downloading webpage
ERROR: Unable to download webpage: <urlopen error Tunnel connection failed: 400 Bad Request> (caused by URLError(error('Tunnel connection failed: 400 Bad Request',),))
  File "/usr/local/bin/youtube-dl/youtube_dl/extractor/common.py", line 627, in _request_webpage
    return self._downloader.urlopen(url_or_request)
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 2237, in urlopen
    return self._opener.open(req, timeout=self._socket_timeout)
  File "/usr/lib/python2.7/urllib2.py", line 429, in open
    response = self._open(req, data)
  File "/usr/lib/python2.7/urllib2.py", line 447, in _open
    '_open', req)
  File "/usr/lib/python2.7/urllib2.py", line 407, in _call_chain
    result = func(*args)
  File "/usr/local/bin/youtube-dl/youtube_dl/utils.py", line 2724, in https_open
    req, **kwargs)
  File "/usr/lib/python2.7/urllib2.py", line 1198, in do_open
    raise URLError(err)

Description

Currently I'm using an HTTP proxy server without HTTP/1.0 support, and since youtube-dl --print-traffic https://youtu.be/3Roz6BVdKcQ prints:

[youtube] 3Roz6BVdKcQ: Downloading webpage
send: u'CONNECT www.youtube.com:443 HTTP/1.0\r\n'
send: '\r\n'
ERROR: Unable to download webpage: <urlopen error Tunnel connection failed: 400 Bad Request> (caused by URLError(error('Tunnel connection failed: 400 Bad Request',),))

I guess that is the problem. My proposal is checking for HTTP/1.1 support before failing to download.

[dstftw]

1.0 is hardcoded in python's httplib. There is no control over it.