title: There are errors when I install django by git?
body: <p>I install django through :</p>
  <blockquote>
  <p>git clone git://github.com/django/django.git</p>
  <p>pip install -e django/</p>
  </blockquote>
  <p>I use Ubuntu 16.04.</p>
  <p>But some errors occur :</p>
  <pre><code>Obtaining file:///home/leo/django
      Complete output from command python setup.py egg_info:
      Traceback (most recent call last):
        File &quot;&lt;string&gt;&quot;, line 1, in &lt;module&gt;
        File &quot;/home/leo/django/setup.py&quot;, line 32, in &lt;module&gt;
          version = __import__('django').get_version()
        File &quot;django/__init__.py&quot;, line 1, in &lt;module&gt;
          from django.utils.version import get_version
        File &quot;django/utils/version.py&quot;, line 60, in &lt;module&gt;
          @functools.lru_cache()
      AttributeError: 'module' object has no attribute 'lru_cache'
      
      ----------------------------------------
  Command &quot;python setup.py egg_info&quot; failed with error code 1 in /home/leo/django/
  </code></pre>
  <p>How to fix this ?
  Thank you.</p>