NoAuthHandlerFound AWS boto ec2 - With env variables set

I am getting what seems to be quite a common error for people starting with AWS, python and boto.

NoAuthHandlerFound: No handler was ready to authenticate. 1 handlers were checked. ['HmacAuthV4Handler'] Check your credentials

I have tried this and this but still get the error.

I know the credentials work and are correct because I have used them to test previous things such as an rds connections.

Script for rds is the following:

import boto.rds as rds
import boto3 as b3
import boto
from sqlalchemy import create_engine

conn = boto.rds.connect_to_region("us-west-2",aws_access_key_id='<ID>',aws_secret_access_key='<KEY>')

engine = create_engine('postgresql://my_id:my_pass@datawarehouse.stuff.us-west-2.rds.amazonaws.com/db_name', echo=False)

res = engine.execute("select * from table")

print res,engine

Which runs without error.

Is there anything I am missing in terms of VPC? Access rights?

Its making me nuts!

I have BOTO_CONFIG set to C:/Users/%USER%/boto.config at the user level (not system level).

and C:/Users/%USER%/boto.config reads as:

[default]
aws_access_key_id = <MY_ID>
aws_secret_access_key = <MY_SECRET>

print boto.__version__

yields:

2.40.0

Thanks for any help.