title: Problem with configuring Netlify CMS with Git Gateway
body: <p>I am trying to use this Gatsby starter with Netlify CMS. <a href="https://github.com/stackrole-dev/gatsby-starter-foundation" rel="noreferrer">https://github.com/stackrole-dev/gatsby-starter-foundation</a></p>
  
  <p>I followed the instructions exactly but after enabling Git Gateway, when I try to login in as admin I encountered this error massage. </p>
  
  <pre><code>Your Git Gateway backend is not returning valid settings. Please make sure it is enabled.
  </code></pre>
  
  <p>I have no ideas why it is not working.</p>
  
  <p>My <code>config.yml</code> is</p>
  
  <pre><code>backend:
    name: git-gateway
    commit_messages:
      create: 'Create {{collection}} “{{slug}}”'
      update: 'Update {{collection}} “{{slug}}”'
      delete: 'Delete {{collection}} “{{slug}}”'
      uploadMedia: '[skip ci] Upload “{{path}}”'
      deleteMedia: '[skip ci] Delete “{{path}}”'
  
  local_backend: true # run npx netlify-cms-proxy-server for local testing
  
  media_folder: "static/assets" 
  public_folder: "/assets" 
  
  collections:
  </code></pre>