title: pytube urllib.error.HTTPError: HTTP Error 403: Forbidden
body: <p>I get an error when i try to download  a video from youtube with pytube.</p>
  
  <pre class="lang-py prettyprint-override"><code>from pytube import YouTube
  
  yt = YouTube('https://www.youtube.com/watch?v=9bZkp7q19f0')
  stream = yt.streams.first()
  stream
  stream.download()
  </code></pre>
  
  <p>The error says "Forbidden", but fetching e.g. with <code>curl</code> from the same URL seems to work just fine. What could be wrong here?</p>
  
  <pre><code>Traceback (most recent call last):
    File "C:/Users/Mr. jarvis/Desktop/youtube/youtube.py", line 7, in &lt;module&gt;
      stream.download()
    File "C:\Users\Mr. jarvis\AppData\Local\Programs\Python\Python37-32\lib\site-packages\pytube\streams.py", line 217, in download
      bytes_remaining = self.filesize
    File "C:\Users\Mr. jarvis\AppData\Local\Programs\Python\Python37-32\lib\site-packages\pytube\streams.py", line 164, in filesize
      headers = request.get(self.url, headers=True)
    File "C:\Users\Mr. jarvis\AppData\Local\Programs\Python\Python37-32\lib\site-packages\pytube\request.py", line 21, in get
      response = urlopen(url)
    File "C:\Users\Mr. jarvis\AppData\Local\Programs\Python\Python37-32\lib\urllib\request.py", line 222, in urlopen
      return opener.open(url, data, timeout)
    File "C:\Users\Mr. jarvis\AppData\Local\Programs\Python\Python37-32\lib\urllib\request.py", line 531, in open
      response = meth(req, response)
    File "C:\Users\Mr. jarvis\AppData\Local\Programs\Python\Python37-32\lib\urllib\request.py", line 641, in http_response
      'http', request, response, code, msg, hdrs)
    File "C:\Users\Mr. jarvis\AppData\Local\Programs\Python\Python37-32\lib\urllib\request.py", line 569, in error
      return self._call_chain(*args)
    File "C:\Users\Mr. jarvis\AppData\Local\Programs\Python\Python37-32\lib\urllib\request.py", line 503, in _call_chain
      result = func(*args)
    File "C:\Users\Mr. jarvis\AppData\Local\Programs\Python\Python37-32\lib\urllib\request.py", line 649, in http_error_default
      raise HTTPError(req.full_url, code, msg, hdrs, fp)
  urllib.error.HTTPError: HTTP Error 403: Forbidden
  </code></pre>