Parses <StateAssignment>

        @param node: Node containing the <StateAssignment> element
        @type node: xml.etree.Element

def parse_state_assignment(self, node):
        """
        Parses <StateAssignment>

        @param node: Node containing the <StateAssignment> element
        @type node: xml.etree.Element
        """

        if 'variable' in node.lattrib:
            variable = node.lattrib['variable']
        else:
            self.raise_error('<StateAssignment> must specify a variable name')

        if 'value' in node.lattrib:
            value = node.lattrib['value']
        else:
            self.raise_error("State assignment for '{0}' must specify a value.",
                             variable)

        action = StateAssignment(variable, value)

        self.current_event_handler.add_action(action)