def METHOD_NAME(self):
    linkpage = self.linkpage_to_page
    linkpage.link_url = 'https://www.rkh.co.uk/'
    self.assertRaisesMessage(
        ValidationError,
        "Linking to both a page and custom URL is not permitted",
        linkpage.clean
    )
    linkpage.link_url = ''
    linkpage.link_page = None
    self.assertRaisesMessage(
        ValidationError,
        "Please choose an internal page or provide a custom URL",
        linkpage.clean
    )
    linkpage.link_page = linkpage
    self.assertRaisesMessage(
        ValidationError,
        "A link page cannot link to another link page",
        linkpage.clean
    )