FIX --output path with spaces fails execution

[allanlaal]

• I've verified and I assure that I'm running youtube-dl 2017.11.26
• [x ] At least skimmed through the README, most notably the FAQ and BUGS sections
• Searched the bugtracker for similar issues including closed ones

bug report:

downloading to a path that has a space " " in it fails execution:

---

[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'-v', u'--default-search', u'ytsearch', u'--no-mtime', u'--no-cache-dir', u'--no-call-home', u'--verbose', u'--ignore-errors', u'--continue', u'--output', u'/afs/Multimedia/Multimedia.SELF/SELF.video.bgmusic/not licensed/%(title)s.%(upload_date)s.[%(uploader)s].%(ext)s', u'--audio-format', u'mp3', u'--audio-quality', u'0', u'--extract-audio', u'--add-metadata', u'']
[debug] Encodings: locale UTF-8, fs UTF-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2017.11.26
[debug] Python version 2.7.12 - Linux-4.10.0-30-generic-x86_64-with-Ubuntu-16.04-xenial
[debug] exe versions: ffmpeg 2.8.11-0ubuntu0.16.04.1, ffprobe 2.8.11-0ubuntu0.16.04.1, rtmpdump 2.4
[debug] Proxy map: {}
[generic] ytsearch:: Requesting header
WARNING: Could not send HEAD request to ytsearch::
[generic] ytsearch:: Downloading webpage
ERROR: Unable to download webpage: (caused by URLError(u'unknown url type: ytsearch',))
File "/usr/local/lib/python2.7/dist-packages/youtube_dl/extractor/common.py", line 506, in _request_webpage
return self._downloader.urlopen(url_or_request)
File "/usr/local/lib/python2.7/dist-packages/youtube_dl/YoutubeDL.py", line 2196, 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 452, in _open
'unknown_open', req)
File "/usr/lib/python2.7/urllib2.py", line 407, in _call_chain
result = func(*args)
File "/usr/lib/python2.7/urllib2.py", line 1266, in unknown_open
raise URLError('unknown url type: %s' % type)

---

[yan12125]

[debug] Command-line args: [u'-v', u'--default-search', u'ytsearch', u'--no-mtime', u'--no-cache-dir', u'--no-call-home', u'--verbose', u'--ignore-errors', u'--continue', u'--output', u'/afs/Multimedia/Multimedia.SELF/SELF.video.bgmusic/not licensed/%(title)s.%(upload_date)s.[%(uploader)s].%(ext)s', u'--audio-format', u'mp3', u'--audio-quality', u'0', u'--extract-audio', u'--add-metadata', u'']

The actual cause is that you didn't specify what to download (see the last argument u''). You may want to recheck your command.