Lambda was unable to configure your environment variables because the environment variables
you have provided contains reserved keys that are currently not supported for modification.
Reserved keys used in this request: AWS_REGION, AWS_ACCESS_KEY
Lambda functions come with a set of default environment variables.
These environment variable names are reserved, and users will not be able to overwrite them.
使用している serverless.yml を確認しないとダメなんだそうだ。。。