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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)

...

""" A context manager that captures stdout/stderr of the current thread. Use it as follows:
        with CaptureOutput() as c:
            ...
        print(c.stdout(), c.stderr())
    """
    orig_stdout = sys.stdout
    orig_stderr = sys.stderr
    orig___stdout = sys.__stdout__
    orig___stderr = sys.__stderr__
    CONTEXTS_BY_THREAD = {}
    class LogStreamIO(io.StringIO):
        def write(self, s):
            if isinstance(s, str) and hasattr(s, 'decode'):
                s = s.decode('unicode-escape')
            return super(CaptureOutput.LogStreamIO, self).write(s)
    def __init__(self):