cfn_gateway_responses_excerpt.yml

x-amazon-apigateway-gateway-responses:
  DEFAULT_4XX:
    defaultResponse: false
    responseParameters:
      gatewayresponse.header.Content-Type: "'application/json'"
    responseTemplates:
      application/json: |
        {
          "code": "$context.error.responseType",
          "message": $context.error.messageString
        }
  DEFAULT_5XX:
    defaultResponse: false
    responseParameters:
      gatewayresponse.header.Content-Type: "'application/json'"
    responseTemplates: 
      application/json: |
        {
          "code": "INTERNAL_ERROR",
          "message": "Internal error"
        }