title: AttributeError: 'module' object has no attribute 'unique'
body: <p>I installed zeroconf on a linux machine running Fedora 20. I have installed all the packages on which zeroconf depends on. However, when I try to run testcert.py, I come across the following error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "./testcert.py", line 49, in &lt;module&gt;
      import _mdns
    File "/opt/home/gcp_cert_test/_mdns.py", line 23, in &lt;module&gt;
      from zeroconf import InterfaceChoice
    File "/usr/lib/python2.7/site-packages/zeroconf-0.17.4-py2.7.egg/zeroconf.py", line 1257, in &lt;module&gt;
      @enum.unique
  AttributeError: 'module' object has no attribute 'unique'
  </code></pre>
  
  <p>Do I need to install any other packages? I am using Python 2.7.</p>