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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)

...

has_been_invoked_before = func_arn in self.function_invoke_times
        
        with self.docker_container_lock:
            env_vars['_LAMBDA_SERVER_PORT'] = str(self.next_port + self.port_offset)
            self.next_port = (self.next_port + 1) % self.max_port
        
        LOG.debug('Priming docker container with runtime "%s" and arn "%s".', runtime, func_arn)
        container_info = self.prime_docker_container(runtime, func_arn, env_vars.items(), lambda_cwd)
        
        
        
        exec_env_vars = ' '.join(['-e {}="${}"'.format(k, k) for (k, v) in env_vars.items()])
        if not command:
            command = '%s %s' % (container_info.entry_point, handler)
        
        copy_command = ''
        docker_cmd = self._docker_cmd()
        if not has_been_invoked_before and config.LAMBDA_REMOTE_DOCKER:
            
            copy_command = '%s cp "%s/." "%s:/var/task";' % (docker_cmd, lambda_cwd, container_info.name)
        cmd = (
            '%s'
            ' %s exec'
            ' %s'  
            ' %s'  
            ' %s'  
        ) % (copy_command, docker_cmd, exec_env_vars, container_info.name, command)
        LOG.debug('Command for docker-reuse Lambda executor: %s' % cmd)
        return cmd
    def startup(self):