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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)

...

""" Helper class to run a shell command in a background thread. """
    def __init__(self, cmd, params={}, outfile=None, env_vars={}, stdin=False,
            quiet=True, inherit_cwd=False, inherit_env=True):
        self.cmd = cmd
        self.process = None
        self.outfile = outfile or os.devnull
        self.stdin = stdin
        self.env_vars = env_vars
        self.inherit_cwd = inherit_cwd
        self.inherit_env = inherit_env
        FuncThread.__init__(self, self.run_cmd, params, quiet=quiet)
    def run_cmd(self, params):
        def convert_line(line):
            line = to_str(line or '')
            return '%s\r\n' % line.strip()
        def filter_line(line):
            """ Return True if this line should be filtered, i.e., not printed """
            return '(Press CTRL+C to quit)' in line
        try:
            self.process = run(self.cmd, asynchronous=True, stdin=self.stdin, outfile=self.outfile,
                env_vars=self.env_vars, inherit_cwd=self.inherit_cwd, inherit_env=self.inherit_env)
            if self.outfile:
                if self.outfile == subprocess.PIPE:
                    
                    streams = ((self.process.stdout, sys.stdout), (self.process.stderr, sys.stderr))
                    for instream, outstream in streams:
                        for line in iter(instream.readline, None):