title: Adding custom headers to all boto3 requests
body: <p>I need to add some custom headers to every boto3 request that is sent out. Is there a way to manage the connection itself to add these headers?</p>
  
  <p>For boto2, <a href="https://kite.com/python/docs/boto.connection.AWSAuthConnection" rel="noreferrer">connection.AWSAuthConnection</a> has a method build_base_http_request which has been helpful. I've yet to find an analogous function within the boto3 documentation though.</p>