youtube-dl urlopen error [Errno 2] Name or service not known

[debug] System config: []
[debug] User config: [u'--output', u'~/\u0388\u03b3\u03b3\u03c1\u03b1\u03c6\u03b1/youtube-dl/%(title)s.%(ext)s']
[debug] Custom config: []
[debug] Command-line args: [u'-v', u'--extract-audio', u'--prefer-ffmpeg', u'--audio-format', u'mp3', u'https://www.youtube.com/watch?v=ygdVEIrVnIk']
[debug] Encodings: locale UTF-8, fs UTF-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2018.02.11
[debug] Python version 2.7.12 (CPython) - Linux-3.19.0-32-generic-x86_64-with-LinuxMint-17.3-rosa
[debug] exe versions: avconv 9.20-6, avprobe 9.20-6, ffmpeg 3.3.3, ffprobe 3.3.3
[debug] Proxy map: {}
[youtube] ygdVEIrVnIk: Downloading webpage
ERROR: Unable to download webpage: <urlopen error [Errno -2] Name or service not known> (caused by URLError(gaierror(-2, 'Name or service not known'),))
  File "/usr/local/bin/youtube-dl/youtube_dl/extractor/common.py", line 519, in _request_webpage
    return self._downloader.urlopen(url_or_request)
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 2199, 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 1089, in https_open
    req, **kwargs)
  File "/usr/lib/python2.7/urllib2.py", line 1198, in do_open
    raise URLError(err)