def METHOD_NAME(self) -> str:
    if self == self.AUTH_FAILURE:
        return ('Failed to access AWS services. Please check your AWS '
                'credentials.')
    elif self == self.AZ_PERMISSION_DENIED:
        return (
            'Failed to retrieve availability zones. '
            'Please ensure that the `ec2:DescribeAvailabilityZones` '
            'action is enabled for your AWS account in IAM. '
            'Ref: https://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_DescribeAvailabilityZones.html.'  # pylint: disable=line-too-long
        )
    else:
        raise ValueError(f'Unknown reason {self}')