title: GitHub ERROR probot: Integration not found, documentation_url
body: <p>I had issues with authentication when working with GitHub's Probot app. When I ran the app using npm start, I would get</p>
  
  <p><code>github: Github request: GET /app/installations - 404 Not Found </code></p>
  
  <p>and</p>
  
  <p><code>ERROR probot: {"message":"Integration not found", "documentation_url": "<a href="https://developer.github.com/v3" rel="noreferrer">https://developer.github.com/v3</a>"} </code></p>
  
  <p>I later found that the reason I was getting this issue was because I was working from a GitHub Enterprise account and needed to add an extra variable to my .env file:</p>
  
  <p><code>GHE_HOST=github.your_company.com </code></p>
  
  <p>After restarting my app, I no longer had those issues.</p>