title: Endless loop incompatible when I pip install requirements (Django1.99)
body: <p><strong>1</strong> I get the warning msg when I pip install my Django project requirements </p>
  
  <blockquote>
    <p>wechat-sdk 0.6.4 has requirement requests==2.6.0, but you'll have
    requests 2.9.1 which is incompatible.</p>
  </blockquote>
  
  <p><strong>2</strong> then follow the tips I uninstall requests and install proper version, but I get another warning</p>
  
  <blockquote>
    <p>python-social-auth 0.2.21 has requirement requests>=2.9.1, but you'll
    have requests 2.6.0 which is incompatible.</p>
  </blockquote>
  
  <p>So, I'm trapped in the endless loop</p>
  
  <p>Can anyone give any advice?  </p>