An AMI must be configured via "ami" (region: #{region})

hawksbill

$ vagrant up --provider=aws
There are errors in the configuration of this machine. Please fix
the following errors and try again:

AWS Provider:
* An AMI must be configured via "ami" (region: #{region})

The issue here is vagrant is not finding the ami information.

The line in the Vagrantfile.
aws.region_config "us-west-2", ami: "ami-53ba502b"