AWS Opsworks connect_to_region returns None

I'm trying to use boto to manage an AWS OpsWorks stack but I can't get the connection and I don't understand why.

With that credentials I can connect to with .ec2 or .sns libs and both are in the same stack's region (eu-west-1).

When I try to connect, conn is None Here's my code:

import boto.opsworks

AWS_ACCESS_KEY_ID = ' ... '

AWS_SECRET_ACCESS_KEY = ' ... '


conn = boto.opsworks.connect_to_region('eu-west-1',
                                      aws_access_key_id=AWS_ACCESS_KEY_ID,
                                      aws_secret_access_key=AWS_SECRET_ACCESS_KEY,
                                      validate_certs=False)

print(conn) # conn is None

conn.describe_layers()

Is it possible to connect to opsworks from outside AWS? Thank you!