title: Use AWS Lambda to start an EC2 instance + provide path to file to be processed
body: <p>I want to write a Lambda function that will start an EC2 instance. That instance should then:</p>
  <ol>
  <li>Download a CSV file from my <code>datadump-input</code> S3 bucket</li>
  <li>Process the file with preloaded Python scripts</li>
  </ol>
  <p><strong>How do I make my EC2 instance download the correct file from S3?</strong> The file name is parsed from the event object and will be different on each run.</p>