Turn x-frame-options tests into CSP tests

IPython/html/services/kernels/tests/test_kernels_api.py

@@ -65,7 +65,7 b' class KernelAPITest(NotebookTestBase):'
         self.assertEqual(r.status_code, 201)
         self.assertIsInstance(kern1, dict)
 
-        self.assertEqual(r.headers['x-frame-options'], "SAMEORIGIN")
+        self.assertEqual(r.headers['Content-Security-Policy'], "frame-ancestors 'self'")
 
     def test_main_kernel_handler(self):
         # POST request
@@ -75,7 +75,7 b' class KernelAPITest(NotebookTestBase):'
         self.assertEqual(r.status_code, 201)
         self.assertIsInstance(kern1, dict)
 
-        self.assertEqual(r.headers['x-frame-options'], "SAMEORIGIN")
+        self.assertEqual(r.headers['Content-Security-Policy'], "frame-ancestors 'self'")
 
         # GET request
         r = self.kern_api.list()