'test_bucket_w_default_event_based_hold' systest is flaky

[tseaver]

From this Kokoro failure:

__________ TestRetentionPolicy.test_bucket_w_default_event_based_hold __________

self = <test_system.TestRetentionPolicy testMethod=test_bucket_w_default_event_based_hold>

 def test_bucket_w_default_event_based_hold(self):
 from google.api_core import exceptions

 new_bucket_name = "w-def-ebh" + unique_resource_id("-")
 self.assertRaises(
 exceptions.NotFound, Config.CLIENT.get_bucket, new_bucket_name
 )
 bucket = retry_429_503(Config.CLIENT.create_bucket)(new_bucket_name)
 self.case_buckets_to_delete.append(new_bucket_name)

 bucket.default_event_based_hold = True
 bucket.patch()

 self.assertTrue(bucket.default_event_based_hold)
 self.assertIsNone(bucket.retention_period)
 self.assertIsNone(bucket.retention_policy_effective_time)
 self.assertFalse(bucket.retention_policy_locked)

 blob_name = "test-blob"
 payload = b"DEADBEEF"
 blob = bucket.blob(blob_name)
 blob.upload_from_string(payload)

 self.case_blobs_to_delete.append(blob)

 other = bucket.get_blob(blob_name)

 self.assertTrue(other.event_based_hold)
 self.assertFalse(other.temporary_hold)
 self.assertIsNone(other.retention_expiration_time)

 with self.assertRaises(exceptions.Forbidden):
 other.delete()

 other.event_based_hold = False
 other.patch()
 other.delete()

 bucket.default_event_based_hold = False
 bucket.patch()

 self.assertFalse(bucket.default_event_based_hold)
 self.assertIsNone(bucket.retention_period)
 self.assertIsNone(bucket.retention_policy_effective_time)
 self.assertFalse(bucket.retention_policy_locked)

 blob.upload_from_string(payload)
> self.assertFalse(blob.event_based_hold)
E AssertionError: True is not false

tests/system/test_system.py:2442: AssertionError

[tseaver]

I'm seeing leaked buckets from this systest, because the blob in them still has its EBH set.