title: While using Travis, why do I get unable to locate credentials in after_deploy
body: <p>So this is my <code>.travis.yml</code>:</p>
  
  <pre><code>language: python
  python:
    - "3.5"
  cache: pip
  install:
    - pip install awscli
  
  script:
    - echo 'test'
  
  deploy:
    provider: s3
    access_key_id: $AWS_ACCESS_ID
    secret_access_key: $AWS_SECRET_ID
    bucket: "xxxxx.com"
    local_dir: build
    skip_cleanup: true
    cache_control: "max-age=21600"
    on:
      branch: master
  
  after_deploy:
    - aws configure set preview.cloudfront true
    - aws cloudfront create-invalidation --distribution-id $CLOUDFRONT_DISTRIBUTION_ID --paths "/*"
  </code></pre>
  
  <p>It is just a html page without node or other framework. I want to push to AWS S3 bucket, and create an invalidation for this bucket's cloudfront.</p>
  
  <p>The problem is, it can upload into AWS S3 bucket successfully, and can't run cloudfront to create invalidation.</p>
  
  <p>I got this error message from Travis.</p>
  
  <pre><code>&gt; Deploying application
  &gt; uploading "index.html" with {:content_type=&gt;"text/html", :cache_control=&gt;"max-age=21600"}
  
  &gt;$ aws configure set preview.cloudfront true
  &gt;$ aws cloudfront create-invalidation --distribution-id $CLOUDFRONT_DISTRIBUTION_ID --paths "/*"
  
  Unable to locate credentials. You can configure credentials by running "aws configure".
  Done.
  </code></pre>
  
  <p>Any thoughts on that?</p>