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# Type of request: This is a ...

[x] bug report
[ ] feature request

# Detailed description

In the `ReceiveMessageResult` of the SQS service, I saw this XML from localstack:

```
...
<MessageAttribute>
     <Name>encoding</Name>
    <Value>
        <DataType>String</DataType>
        <StringValue><![CDATA[gzip]]></StringValue>
    </Value>
</MessageAttribute>
...
```

The `<![CDATA[gzip]]>` is slightly different from AWS, which doesn't wrap the value in a `<!CDATA[[]]>` section. This shouldn't be a problem for XML parsers that accept both plain characters and CDATA sections for this element, but the XML parser I was using did not, which causes an error when running the code against localstack but not when running the code against AWS. There is obviously a bug in the XML parser as well, but I thought that I should at least post this here since it is different than what AWS SQS does.

## Expected behavior

MessageAttribute::Value elements should not be wrapped in `CDATA` sections.

## Actual behavior

MessageAttribute::Value elements all seem to be wrapped in `CDATA` sections.

# Steps to reproduce

Send a message to the SQS service which contains some custom message attributes, then make a ReceiveMessageRequest.

## Command used to start LocalStack

`docker run --env "SERVICES=sqs" localstack/localstack`

## Client code (AWS SDK code snippet, or sequence of "awslocal" commands)

...

client = self.client
        response = client.create_queue(QueueName='test-queue')
        queue_url = response['QueueUrl']
        try:
            client.send_message_batch(QueueUrl=queue_url, Entries=[])
        except ClientError as e:
            self.assertEqual(e.response['Error']['Code'], 'EmptyBatchRequest')
            self.assertIn(e.response['ResponseMetadata']['HTTPStatusCode'], [400, 404])
        entries = [{
            'Id': 'message{:02d}'.format(0),
            'MessageBody': 'msgBody{:02d}'.format(0),
            'MessageAttributes': {
                'CustomAttribute': {
                    'DataType': 'String',
                    'StringValue': 'CustomAttributeValue{:02d}'.format(0)
                }
            }
        }]
        result = client.send_message_batch(QueueUrl=queue_url, Entries=entries)
        self.assertEqual(result['ResponseMetadata']['HTTPStatusCode'], 200)
        
        client.delete_queue(QueueUrl=queue_url)