title: urllib2.HTTPError: HTTP Error 403: SSL is required when installing nltk==2.0.5
body: <p>When installing nltk==2.0.5, I get the error <code>urllib2.HTTPError: HTTP Error 403: SSL is required</code>. Really, I'm trying to install <code>newspaper</code>, but it's failing when trying to install this package.</p>
  
  <p>A minimal Dockerfile to reproduce the issue:</p>
  
  <pre><code>FROM ubuntu:16.04
  
  RUN apt-get update
  RUN apt-get install -y python-pip
  
  # problem occurs with or without the following line
  RUN pip install --upgrade pip
  
  CMD ["pip", "install", "nltk==2.0.5"]
  </code></pre>