title: InsecurePlatformWarning when building Docker image
body: <p>I get this warning when building my Docker image:</p>
  
  <pre><code>/usr/local/lib/python2.7/dist-packages/requests/packages/urllib3/util/ssl_.py:79: 
        InsecurePlatformWarning: A true SSLContext object is not available. 
        This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail. 
        For more information, see https://urllib3.readthedocs.org/en/latest/security.html#insecureplatformwarning.
  </code></pre>
  
  <p>Several sources (like <a href="https://stackoverflow.com/questions/29134512/insecureplatformwarning-a-true-sslcontext-object-is-not-available-this-prevent">InsecurePlatformWarning: A true SSLContext object is not available. This prevents urllib3 from configuring SSL appropriately</a>) say that <code>pip install pyopenssl ndg-httpsclient pyasn1</code> will fix this issue. But I get the warning as soon as pip attemps to install pyopenssl.</p>
  
  <p>Here's my Dockerfile:</p>
  
  <pre><code>FROM ubuntu:14.04
  
  # Install packages
  RUN apt-get update &amp;&amp; apt-get install -y \
      git \
      libmysqlclient-dev \
      mysql-server \
      nginx \
      python-dev \
      python-mysqldb \
      python-setuptools \
      supervisor \
      vim
  RUN easy_install pip
  
  # Handle urllib3 InsecurePlatformWarning
  RUN apt-get install -y libffi-dev libssl-dev
  RUN pip install pyopenssl ndg-httpsclient pyasn1
  
  # ...more
  </code></pre>