title: copy file from gcs to s3 in boto3
body: <p>I am looking to copy files from gcs to my s3 bucket. In boto2, easy as a button.</p>
  
  <pre><code>conn = connect_gs(user_id, password)
  gs_bucket = conn.get_bucket(gs_bucket_name) 
  for obj in bucket:
     s3_key = key.Key(s3_bucket)
     s3_key.key = obj
     s3_key.set_contents_from_filename(obj)
  </code></pre>
  
  <p>However in boto3, I am lost trying to find equivalent code. Any takers?</p>