PostgreSQL Permissions in Amazon RDS using Flyway Migration

I'm trying to get Flyway up and running for database source control of Postgres and am running into permissions issues.

Scenario: New database on AWS RDS PostgreSQL instance.

• RDS superuser configured is "postgres" and I login as that to create the db and setup roles.

• I create a "flyway_user" account that I want the flyway tool to use and add it to the rds_superuser role.

• I create a couple schemas that flyway will manage and GRANT ALL ON SCHEMA to the "flyway_user" account.

When I then try to have flyway to a migration to create tables in these schemas I get an error of permission denied. So what am I missing here? Thanks in advance for any advice.