new_contents: from unittest import TestCase
  
  from openelex.base.fetch import ErrorHandlingURLopener, HTTPError
  
  class TestErrorHandlingURLopener(TestCase):
      def setUp(self):
          self.opener = ErrorHandlingURLopener()
  
      def test_404(self):
          url = "http://example.com/test.csv"
          self.assertRaises(HTTPError, self.opener.retrieve, url)
  
subject: Add missing test for ErrorHandlingURLopener