title: ImportError: cannot import name cached_property
body: <p>I am trying to set up Tipfy extensions on a Python/Google App Engine project that I've been brought in on. I have followed all the instructions for running bootstrap.py and then bin/buildout. Everything seems to have worked but now when I try to import tipfy.ext.auth, I get this error:</p>
  
  <pre><code>File "C:\{project}\app\lib\dist\tipfy\ext\auth\__init__.py", line 15, in &lt;module&gt;
      from tipfy import abort, cached_property, import_string, redirect
  ImportError: cannot import name cached_property
  </code></pre>
  
  <p>I'm a bit lost now and don't really know where to even look for the solution to this as I am, admittedly, very new to both Python and GAE. Any help or direction on how to get this extension working would be greatly appreciated.</p>