new_contents: import requests
  
  from notebook.notebookapp import NotebookApp
  from notebook.tests.launchnotebook import NotebookTestBase
  from notebook.utils import url_path_join
  from traitlets.config import Config
  
  
  class ConfiguratorTest(NotebookTestBase):
  
      config = Config(log_level='DEBUG')
      if hasattr( NotebookApp, 'nbserver_extensions'):
          config.nbserver_extensions = Config({
              'themysto.nbextensions_configurator': True,
          })
      else:
          config.server_extensions = [
              'themysto.nbextensions_configurator',
          ]
  
      def test_load_nbextensions_page(self):
          """check that /nbextensions url loads"""
          response = requests.request(
              'GET', url_path_join(self.base_url(), 'nbextensions'),
          )
          response.raise_for_status()
  
subject: check that `{base_url}/nbextensions` page loads