This has finally been added to AWSCLI: https://docs.aws.amazon.com/cli/latest/reference/cognito-idp/admin-set-user-password.html
You can change a user’s password and update status using:
aws cognito-idp admin-set-user-password \
--user-pool-id <your-user-pool-id> \
--username <username> \
--password <password> \
--permanent
Before using this, you may need to update your AWS CLI using:
pip3 install awscli --upgrade