[core] Disable flaky cancellation test (#9325)

python/ray/tests/test_cancel.py

@@ -1,10 +1,12 @@
-import pytest
-import ray
 import random
 import sys
 import time
-from ray.exceptions import RayTaskError, RayTimeoutError, \
-                            RayCancellationError, RayWorkerError
+
+import pytest
+
+import ray
+from ray.exceptions import RayCancellationError, RayTaskError, \
+                           RayTimeoutError, RayWorkerError
 from ray.test_utils import SignalActor
 
 
@@ -154,7 +156,9 @@ def test_comprehensive(ray_start_regular, use_force):
         ray.get(combo)
 
 
-@pytest.mark.parametrize("use_force", [True, False])
+# Running this test with use_force==False is flaky.
+# TODO(ilr): Look into the root of this flakiness.
+@pytest.mark.parametrize("use_force", [True])
 def test_stress(shutdown_only, use_force):
     ray.init(num_cpus=1)
 
@@ -180,9 +184,7 @@ def test_stress(shutdown_only, use_force):
     for done in cancelled:
         with pytest.raises(valid_exceptions(use_force)):
             ray.get(done)
-
-    for indx in range(len(tasks)):
-        t = tasks[indx]
+    for indx, t in enumerate(tasks):
         if sleep_or_no[indx]:
             ray.cancel(t, use_force)
             cancelled.add(t)