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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)

...

import os
import logging
import traceback
from moto.sqs import responses as sqs_responses
from moto.sqs.models import Queue
from localstack import config
from localstack.config import LOCALSTACK_HOSTNAME, TMP_FOLDER
from localstack.utils.aws import aws_stack
from localstack.utils.common import wait_for_port_open, save_file, short_uid, TMP_FILES, get_free_tcp_port
from localstack.services.sqs import sqs_listener
from localstack.services.infra import start_proxy_for_service, get_service_protocol, do_run, start_moto_server
from localstack.services.install import INSTALL_DIR_ELASTICMQ, install_elasticmq
LOG = logging.getLogger(__name__)
PORT_SQS_BACKEND = None
MAX_HEAP_SIZE = '256m'
def check_sqs(expect_shutdown=False, print_error=False):
    out = None
    try:
        
        wait_for_port_open(PORT_SQS_BACKEND)
        
        out = aws_stack.connect_to_service(service_name='sqs').list_queues()
    except Exception as e:
        if print_error:
            LOG.warning('SQS health check failed: %s %s' % (e, traceback.format_exc()))
    if expect_shutdown:
        assert out is None
    else:
        assert out.get('ResponseMetadata', {}).get('HTTPStatusCode') == 200
def start_sqs(*args, **kwargs):