Do not raise exception If "domainName" is not present.

[purple4reina]

What does this PR do?

Motivation

The generic test "API Gateway AWS Proxy" event does not have requestContext.domainName. Without it, the layer raises an exception and logs it.

{ "body": "eyJ0ZXN0IjoiYm9keSJ9", "resource": "/{proxy+}", "path": "/path/to/resource", "httpMethod": "POST", "isBase64Encoded": true, "queryStringParameters": { "foo": "bar" }, "multiValueQueryStringParameters": { "foo": [ "bar" ] }, "pathParameters": { "proxy": "/path/to/resource" }, "stageVariables": { "baz": "qux" }, "headers": { "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8", "Accept-Encoding": "gzip, deflate, sdch", "Accept-Language": "en-US,en;q=0.8", "Cache-Control": "max-age=0", "CloudFront-Forwarded-Proto": "https", "CloudFront-Is-Desktop-Viewer": "true", "CloudFront-Is-Mobile-Viewer": "false", "CloudFront-Is-SmartTV-Viewer": "false", "CloudFront-Is-Tablet-Viewer": "false", "CloudFront-Viewer-Country": "US", "Host": "1234567890.execute-api.us-east-1.amazonaws.com", "Upgrade-Insecure-Requests": "1", "User-Agent": "Custom User Agent String", "Via": "1.1 08f323deadbeefa7af34d5feb414ce27.cloudfront.net (CloudFront)", "X-Amz-Cf-Id": "cDehVQoZnx43VYQb9j2-nvCh-9z396Uhbp027Y2JvkCPNLmGJHqlaA==", "X-Forwarded-For": "127.0.0.1, 127.0.0.2", "X-Forwarded-Port": "443", "X-Forwarded-Proto": "https" }, "multiValueHeaders": { "Accept": [ "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8" ], "Accept-Encoding": [ "gzip, deflate, sdch" ], "Accept-Language": [ "en-US,en;q=0.8" ], "Cache-Control": [ "max-age=0" ], "CloudFront-Forwarded-Proto": [ "https" ], "CloudFront-Is-Desktop-Viewer": [ "true" ], "CloudFront-Is-Mobile-Viewer": [ "false" ], "CloudFront-Is-SmartTV-Viewer": [ "false" ], "CloudFront-Is-Tablet-Viewer": [ "false" ], "CloudFront-Viewer-Country": [ "US" ], "Host": [ "0123456789.execute-api.us-east-1.amazonaws.com" ], "Upgrade-Insecure-Requests": [ "1" ], "User-Agent": [ "Custom User Agent String" ], "Via": [ "1.1 08f323deadbeefa7af34d5feb414ce27.cloudfront.net (CloudFront)" ], "X-Amz-Cf-Id": [ "cDehVQoZnx43VYQb9j2-nvCh-9z396Uhbp027Y2JvkCPNLmGJHqlaA==" ], "X-Forwarded-For": [ "127.0.0.1, 127.0.0.2" ], "X-Forwarded-Port": [ "443" ], "X-Forwarded-Proto": [ "https" ] }, "requestContext": { "accountId": "123456789012", "resourceId": "123456", "stage": "prod", "requestId": "c6af9ac6-7b61-11e6-9a41-93e8deadbeef", "requestTime": "09/Apr/2015:12:34:56 +0000", "requestTimeEpoch": 1428582896000, "identity": { "cognitoIdentityPoolId": null, "accountId": null, "cognitoIdentityId": null, "caller": null, "accessKey": null, "sourceIp": "127.0.0.1", "cognitoAuthenticationType": null, "cognitoAuthenticationProvider": null, "userArn": null, "userAgent": "Custom User Agent String", "user": null }, "path": "/prod/path/to/resource", "resourcePath": "/{proxy+}", "httpMethod": "POST", "apiId": "1234567890", "protocol": "HTTP/1.1" } }

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