Create an ``lxml``-based HTML DOM from the response. The tree
        will not have a root, so all queries need to be relative
        (i.e. start with a dot).

def html(self):
        """ Create an ``lxml``-based HTML DOM from the response. The tree
        will not have a root, so all queries need to be relative
        (i.e. start with a dot).
        """
        try:
            from lxml import html
            return html.fromstring(self.content)
        except ImportError as ie:
            raise DependencyException(ie)