Deleting a non-existent key through s3api's delete-objects should return a valid response..

```
aws s3api delete-objects --bucket my-bucket --delete '{\"Objects\":[{\"Key\":\"my-key\"}]}'
```
Gives...
```
{
    "Deleted": [
        {
            "Key": "my-key"
        }
    ]
}
```

Deleting a non-existent key through s3api's delete-objects on LocalStack returns an error response without any additional information beyond the key.

```
aws s3api delete-objects --bucket my-bucket --delete '{"Objects":[{"Key":"my-key"}]}' --endpoint-url http://localhost:4572
```
Gives...
```
{
    "ResponseMetadata": {
        "HTTPStatusCode": 200,
        "HTTPHeaders": {
            "server": "BaseHTTP/0.6 Python/3.7.5",
            "date": "Fri, 20 Dec 2019 16:02:39 GMT",
            "content-type": "application/xml; charset=utf-8",
            "content-length": "180",
            "access-control-allow-origin": "*",
            "last-modified": "Fri, 20 Dec 2019 16:02:39 GMT",
            "access-control-allow-methods": "HEAD,GET,PUT,POST,DELETE,OPTIONS,PATCH",
            "access-control-allow-headers": "authorization,content-type,content-md5,cache-control,x-amz-content-sha256,x-amz-date,x-amz-security-token,x-amz-user-agent,x-amz-target,x-amz-acl,x-amz-version-id,x-localstack-target,x-amz-tagging",
            "access-control-expose-headers": "x-amz-version-id"
        },
        "RetryAttempts": 0
    },
    "Errors": [
        {
            "Key": "my-key"
        }
    ]
}
```

Deleting an existent key seems to work fine.
if 'Range' not in headers:
        return
    s3_client = aws_stack.connect_to_service('s3')
    key_name = get_key_name(path, headers)
    result = s3_client.head_object(Bucket=bucket_name, Key=key_name)
    content_type = result['ContentType']
    if response.headers.get('Content-Type') == 'text/html; charset=utf-8':
        response.headers['Content-Type'] = content_type
def remove_xml_preamble(response):
    """ Removes <?xml ... ?> from a response content """
    response._content = re.sub(r'^<\?[^\?]+\?>', '', response._content)
def get_lifecycle(bucket_name):
    bucket_name = normalize_bucket_name(bucket_name)
    lifecycle = BUCKET_LIFECYCLE.get(bucket_name)
    status_code = 200
    if not lifecycle:
        
        lifecycle = {
            'Error': {
                'Code': 'NoSuchLifecycleConfiguration',
                'Message': 'The lifecycle configuration does not exist'
            }
        }
        status_code = 404
    body = xmltodict.unparse(lifecycle)
    return requests_response(body, status_code=status_code)
def get_replication(bucket_name):