title: Cloud Pub/Sub: HTTP URL is not registered even after domain is registered
body: <p>I have a Google Pub/Sub project and created a topic and a simple subscription. </p>
  
  <p>However, when specifying a URL for push, I keep getting the error below.  I have completed the site verification process and registered the domain in APIs &amp; services as described in <a href="https://cloud.google.com/pubsub/docs/push#other-endpoints" rel="noreferrer">https://cloud.google.com/pubsub/docs/push#other-endpoints</a>: </p>
  
  <pre><code>ERROR: Failed to create subscription [projects/&lt;project-id&gt;/subscriptions/my-sub-2]: The supplied HTTP URL is not registered in the subscription's parent project (url="https://us-central1-&lt;project-id&gt;.cloudfunctions.net/xxxx", project_id="&lt;project id number&gt;").
  ERROR: (gcloud.pubsub.subscriptions.create) Failed to create the following: [my-sub-2].
  </code></pre>
  
  <p>Please help !!</p>