Fix flaky GCS bucket deletion in test_create_default_bucket (#36786)

* Handle NotFound exception in bucket deletion test

* Added retry logic for bucket

Author: aIbrahiim

sdks/python/apache_beam/io/gcp/gcsio_integration_test.py

@@ -242,9 +242,27 @@ def test_create_default_bucket(self, mock_default_gcs_bucket_name):
     # verify soft delete policy is disabled by default in the default bucket
     # after creation
     self.assertEqual(bucket.soft_delete_policy.retention_duration_seconds, 0)
-    bucket.delete()
-
-    self.assertIsNone(self.gcsio.get_bucket(overridden_bucket_name))
+    max_retries = 5
+    retry_delay = 1
+    existing_bucket = None
+    for attempt in range(max_retries):
+      try:
+        existing_bucket = self.gcsio.get_bucket(overridden_bucket_name)
+        break
+      except NotFound:
+        if attempt < max_retries - 1:
+          time.sleep(retry_delay)
+          retry_delay *= 2
+        else:
+          existing_bucket = None
+    if existing_bucket:
+      try:
+        existing_bucket.delete()
+      except NotFound:
+        pass
+    time.sleep(WAIT_BUCKET_PROPAGATION_SECONDS)
+    with self.assertRaises(NotFound):
+      self.gcsio.get_bucket(overridden_bucket_name)
 
 
 class GcsIOReadGzipTest(unittest.TestCase):