I've created a Lambda that check on a DynamoDB table the existence of a record matching host and request path and, if found, returns a redirect to the matching URL.

My Lambda returns this response but the ALB returns 502.
```
{
"statusCode": 301,
"statusDescription": null,
"headers": {
"Location": "https://www.my-target.co.uk/"
},
"multiValueHeaders": null,
"body": "Redirecting to https://www.my-target.co.uk/",
"isBase64Encoded": false
}
```

This is the log I find in CloudWatch for the Lambda function
```
START RequestId: 8b5a28f2-c56d-4418-a7b9-66ebe0ba2470 Version: $LATEST
[Information] EMG.ApplicationLoadBalancerRequestHandler: Received: GET /
[Information] EMG.ApplicationLoadBalancerRequestHandler: Processing: my-test.net /
[Information] EMG.RedirectManagers.RedirectTableRedirectManager: Fetching item: my-test.net / from table redirect-table
[Information] EMG.ApplicationLoadBalancerRequestHandler: Found: https://www.target.co.uk/ Permanent
END RequestId: 8b5a28f2-c56d-4418-a7b9-66ebe0ba2470
REPORT RequestId: 8b5a28f2-c56d-4418-a7b9-66ebe0ba2470 Duration: 69.59 ms Billed Duration: 100 ms Memory Size: 128 MB Max Memory Used: 39 MB
```

This is the response I get

```
HTTP/1.1 502
status: 502
Server: awselb/2.0
Date: Thu, 15 Aug 2019 19:13:58 GMT
Content-Type: text/html
Content-Length: 138
Connection: keep-alive

502 Bad Gateway

502 Bad Gateway

I couldn't find anything saying we can't return non-200 responses from Lambda, so I really have no idea...

Start with the AWS Application Load Balancer Lambda response contract and the provided response, focusing on the null statusDescription and the 301 redirect. Trace how this repository handles statusCode and statusDescription, then verify the required status-code/reason-phrase format and the resulting non-200 response behavior.

Written by the indexing model from the issue text.