xfail(LearnerND) for test_learner_performance_is_invariant_under_scaling

adaptive/tests/test_learners.py

@@ -362,7 +362,9 @@ def test_expected_loss_improvement_is_less_than_total_loss(learner_type, f, lear
 
 # XXX: This *should* pass (https://gitlab.kwant-project.org/qt/adaptive/issues/84)
 #      but we xfail it now, as Learner2D will be deprecated anyway
-@run_with(Learner1D, xfail(Learner2D), LearnerND)
+# The LearnerND fails sometimes, see
+# https://gitlab.kwant-project.org/qt/adaptive/merge_requests/128#note_21807
+@run_with(Learner1D, xfail(Learner2D), xfail(LearnerND))
 def test_learner_performance_is_invariant_under_scaling(learner_type, f, learner_kwargs):
     """Learners behave identically under transformations that leave
        the loss invariant.