code: def ui(root_url, path):
      
      root_url = root_url.rstrip('/')
      path = path.lstrip('/')
      if root_url == OLD_ROOT_URL:
          return 'https://tools.taskcluster.net/{}'.format(path)
      else:
          return '{}/{}'.format(root_url, path)
docs: Generate URL for a path in the Taskcluster ui.
      The purpose of the function is to switch on rootUrl:
      "The driver for having a ui method is so we can just call ui with a path and any root url,
      and the returned url should work for both our current deployment (with root URL = https://taskcluster.net)
      and any future deployment. The returned value is essentially rootURL == 'https://taskcluster.net'
      'https://tools.taskcluster.net/${path}'
      '${rootURL}/${path}' "