title: Python Error:No host specified
body: <p>I just wrote a simple python demo,while met a confusing problem.</p>
  
  <pre><code>import requests
  
  print(requests.get('http://www.sina.com.cn/'))
  </code></pre>
  
  <p>I know that right result is return Response [200].But in my WIN10 x64,it returns the following error,I guess maybe some problems occur in my computer.</p>
  
  <pre><code>Traceback (most recent call last):
    File "C:\Users\CJY\Desktop\Python_Demo\web.py", line 2, in &lt;module&gt;
      print(requests.get('http://www.sina.com.cn/'))
    File "D:\python3.6.1\lib\site-packages\requests\api.py", line 72, in get
      return request('get', url, params=params, **kwargs)
    File "D:\python3.6.1\lib\site-packages\requests\api.py", line 58, in request
      return session.request(method=method, url=url, **kwargs)
    File "D:\python3.6.1\lib\site-packages\requests\sessions.py", line 518, in request
      resp = self.send(prep, **send_kwargs)
    File "D:\python3.6.1\lib\site-packages\requests\sessions.py", line 639, in send
      r = adapter.send(request, **kwargs)
    File "D:\python3.6.1\lib\site-packages\requests\adapters.py", line 403, in send
      conn = self.get_connection(request.url, proxies)
    File "D:\python3.6.1\lib\site-packages\requests\adapters.py", line 302, in get_connection
      conn = proxy_manager.connection_from_url(url)
    File "D:\python3.6.1\lib\site-packages\requests\packages\urllib3\poolmanager.py", line 279, in connection_from_url
      pool_kwargs=pool_kwargs)
    File "D:\python3.6.1\lib\site-packages\requests\packages\urllib3\poolmanager.py", line 408, in connection_from_host
      self.proxy.host, self.proxy.port, self.proxy.scheme, pool_kwargs=pool_kwargs)
    File "D:\python3.6.1\lib\site-packages\requests\packages\urllib3\poolmanager.py", line 218, in connection_from_host
      raise LocationValueError("No host specified.")
  requests.packages.urllib3.exceptions.LocationValueError: No host specified.
  [Finished in 0.2s]
  </code></pre>
  
  <p>Please help me!</p>