title: Gcm api key fails authentication in IPV6
body: <p>I am trying to send push notification to android device using python gcm, but in my server it always fails to authenticate, I'd tried to create a new server api key with Server IP address and tried </p>
  
  <pre><code>curl --header "Authorization: key =$api_key" --header Content-Type:"application/json" https://android.googleapis.com/gcm/send  -d "{\"registration_ids\":[\"ABC\"]}"
  </code></pre>
  
  <p>but it shows</p>
  
  <pre><code>&lt;TITLE&gt;Unauthorized&lt;/TITLE&gt;
  &lt;BODY BGCOLOR="#FFFFFF" TEXT="#000000"&gt;
  &lt;H1&gt;Unauthorized&lt;/H1&gt;
  &lt;H2&gt;Error 401&lt;/H2&gt;
  &lt;/BODY&gt;
  &lt;/HTML&gt;
  </code></pre>
  
  <p>but when i tried with creating a new api key without any IP specified it worked and shows</p>
  
  <pre><code>{"multicast_id":8030697046624335774,"success":0,"failure":1,"canonical_ids":0,"results":[{"error":"InvalidRegistration"}]}
  </code></pre>
  
  <p>So I'm unable to send notification using api key with restricted IP but it works without giving any IP. The known issue issue is that Server IP is IPV6, and found that there is some trouble sending GCM via IPV6. Could anyone help me to solve this? </p>