On boto I used to specify my credentials when connecting to S3 in such a way:
import boto from boto.s3.connection import Key, S3Connection S3 = S3Connection(
You can get a client with new session directly like below.
client
s3_client = boto3.client('s3', aws_access_key_id=settings.AWS_SERVER_PUBLIC_KEY, aws_secret_access_key=settings.AWS_SERVER_SECRET_KEY, region_name=REGION_NAME )