test(streaming): make bucket get_safe_version test actually exercise the except branch

The prior test patched _load_metadata as a plain no-op, so __init__'s try
block succeeded and never entered the except branch where the
repo_type != "bucket" guard and get_safe_version live - the assertion passed
vacuously (verified: it still passed with the guard removed).

Use side_effect=[FileNotFoundError, None] so the first _load_metadata raises
(forcing the except path) and the second succeeds after the meta pull, and
stub _pull_from_repo so the path runs without a network call. Now the test
fails if the bucket guard is removed. Thanks @mohitydv09 for the catch.

Signed-off-by: Sundar Raghavan <sdraghav@amazon.com>

tests/datasets/test_streaming.py

@@ -495,16 +495,30 @@ def test_bucket_metadata_url_root(tmp_path):
 
 
 def test_bucket_skips_get_safe_version(tmp_path):
-    """repo_type='bucket' must NOT call get_safe_version (buckets have no git refs)."""
+    """repo_type='bucket' must NOT call get_safe_version (buckets have no git refs).
-    mock_fs = MagicMock()
+
+    The first ``_load_metadata()`` raises ``FileNotFoundError`` so ``__init__``
+    enters the except branch where the ``repo_type != "bucket"`` guard and
+    ``get_safe_version`` live; the second call (after the bucket meta pull)
+    succeeds. ``_pull_from_repo`` is stubbed so the except path runs without a
+    network call. Without the raise, the try block would succeed and the guard
+    branch would never execute, so the assertion would pass vacuously.
+    """
     with (
         patch("lerobot.datasets.dataset_metadata.get_safe_version") as mock_gsv,
-        patch("huggingface_hub.HfFileSystem", return_value=mock_fs),
+        patch.object(
-        patch.object(LeRobotDatasetMetadata, "_load_metadata"),
+            LeRobotDatasetMetadata,
+            "_load_metadata",
+            side_effect=[FileNotFoundError, None],
+        ),
+        patch.object(LeRobotDatasetMetadata, "_pull_from_repo") as mock_pull,
     ):
         LeRobotDatasetMetadata(
             DUMMY_REPO_ID,
             root=tmp_path,
             repo_type="bucket",
         )
+    # The except branch ran (proven by the pull), but the bucket guard skipped
+    # version resolution.
+    mock_pull.assert_called_once()
     mock_gsv.assert_not_called()