title: Google Discovery API The request is missing a valid API key
body: <p>We've been using the google discovery api for analytics setup to make the request: "<a href="https://analytics.googleapis.com/" rel="noreferrer">https://analytics.googleapis.com/</a>$discovery/rest?version=v4"
  This has been working fine for over two years now, however just today it's started responding with: </p>
  
  <pre><code>googleapiclient.errors.HttpError: &lt;HttpError 403 when requesting https://analytics.googleapis.com/$discovery/rest?version=v4 returned "The request is missing a valid API key."&gt;
  </code></pre>
  
  <p>I cannot seem to find any status on this api but I feel as if something might have changed.</p>
  
  <p>Manual testing has been performed and I've replicated the issue consistently.</p>
  
  <pre><code>&gt;&gt;&gt; credentials = oauth2client.client.GoogleCredentials("&lt;redacted&gt;", "&lt;redacted&gt;", "&lt;redacted&gt;", "&lt;redacted&gt;", None, "https://accounts.google.com/o/oauth2/token", "UserAgentHere")
  
  &gt;&gt;&gt; credentials
  &lt;oauth2client.client.GoogleCredentials object at 0x7f533eaf60b8&gt;
  
  &gt;&gt;&gt; import httplib2
  
  &gt;&gt;&gt; http = credentials.authorize(http=httplib2.Http())
  
  &gt;&gt;&gt; http
  &lt;httplib2.Http object at 0x7f533eaf6390&gt;
  
  &gt;&gt;&gt; from apiclient.discovery import build
  
  &gt;&gt;&gt; build("analytics", "v4", http=http, cache_discovery=False)
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
    File "/usr/lib/python3.6/site-packages/googleapiclient/_helpers.py", line 130, in positional_wrapper
      return wrapped(*args, **kwargs)
    File "/usr/lib/python3.6/site-packages/googleapiclient/discovery.py", line 232, in build
      raise e
    File "/usr/lib/python3.6/site-packages/googleapiclient/discovery.py", line 224, in build
      requested_url, discovery_http, cache_discovery, cache, developerKey)
    File "/usr/lib/python3.6/site-packages/googleapiclient/discovery.py", line 277, in _retrieve_discovery_doc
      raise HttpError(resp, content, uri=actual_url)
  googleapiclient.errors.HttpError: &lt;HttpError 403 when requesting https://analytics.googleapis.com/$discovery/rest?version=v4 returned "The request is missing a valid API key."&gt;
  &gt;&gt;&gt;
  </code></pre>