Auto search thinks queries with slash are URLs automatically

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Checklist

• I'm reporting a broken site support issue
• I've verified that I'm running youtube-dl version 2019.07.16
• 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

λ youtube-dl --default-search=auto "Bud Powell - You go to my head / remastered" -v
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['--default-search=auto', 'Bud Powell - You go to my head / remastered', '-v']
[debug] Encodings: locale cp1252, fs utf-8, out utf-8, pref cp1252
[debug] youtube-dl version 2019.07.16
[debug] Python version 3.7.3 (CPython) - Windows-10-10.0.17134-SP0
[debug] exe versions: ffmpeg N-94300-gaf5f770113, ffprobe N-94300-gaf5f770113
[debug] Proxy map: {}
WARNING: The url doesn't specify the protocol, trying with http
[generic]  remastered: Requesting header
WARNING: Could not send HEAD request to http://Bud Powell - You go to my head / remastered: <urlopen error [Errno 11001] getaddrinfo failed>
[generic]  remastered: Downloading webpage
ERROR: Unable to download webpage: <urlopen error [Errno 11001] getaddrinfo failed> (caused by URLError(gaierror(11001, 'getaddrinfo failed')))
  File "c:\users\stavl\envs\spotify-queue-playlist\lib\site-packages\youtube_dl\extractor\common.py", line 627, in _request_webpage
    return self._downloader.urlopen(url_or_request)
  File "c:\users\stavl\envs\spotify-queue-playlist\lib\site-packages\youtube_dl\YoutubeDL.py", line 2227, in urlopen
    return self._opener.open(req, timeout=self._socket_timeout)
  File "c:\users\stavl\appdata\local\programs\python\python37-32\Lib\urllib\request.py", line 525, in open
    response = self._open(req, data)
  File "c:\users\stavl\appdata\local\programs\python\python37-32\Lib\urllib\request.py", line 543, in _open
    '_open', req)
  File "c:\users\stavl\appdata\local\programs\python\python37-32\Lib\urllib\request.py", line 503, in _call_chain
    result = func(*args)
  File "c:\users\stavl\envs\spotify-queue-playlist\lib\site-packages\youtube_dl\utils.py", line 2568, in http_open
    req)
  File "c:\users\stavl\appdata\local\programs\python\python37-32\Lib\urllib\request.py", line 1319, in do_open
    raise URLError(err)

Description

Whenever you try to download a song using the --default-search=auto feature, everything works fine and it detects if the query given is not a URL, and if so it searches it.

But, if there's a slash character in the query, it automatically thinks the given string is a URL (as shown in my example wih "Bud Powell - You Go To My Head / Remastered". It thinks a URL was given, tries to append http:// to the query, and gets a very invalid URL.

Possible workaround until this is fixed:

• Specify the search option explicitly
• Strip the queries of slashes if they aren't URLs