[c-c schema] devtools: the output file for cw-ctl schema is not supposed to exist When using the 'file' type, logilab-common errors out if the file doesn't exist. Which, if the option refers to an output file, is not so useful. Use 'string' instead.

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  <div class="ajaxHtmlHead">
    <script src="http://foo.js" type="text/javascript"> </script>
  </div>
  <h1>Hello</h1>
</div>