Parses <OnCondition>

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

def parse_on_condition(self, node):
        """
        Parses <OnCondition>

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

        try:
            test = node.lattrib['test']
        except:
            self.raise_error('<OnCondition> must specify a test.')
            
        event_handler = OnCondition(test)

        self.current_regime.add_event_handler(event_handler)

        self.current_event_handler = event_handler
        self.process_nested_tags(node)
        self.current_event_handler = None