refactor(jobs): use HF_LEROBOT_HOME constant for the local cache root

Resolve the local dataset cache via lerobot.utils.constants.HF_LEROBOT_HOME
instead of re-reading the env var by hand, dropping the os/Path imports.
Tests now patch the imported constant and assert on a stable message
substring (the previous "neither" match only passed by accident, matching
the test name embedded in the pytest tmp_path).

src/lerobot/jobs/dataset.py

@@ -21,10 +21,10 @@ local-only dataset is pushed to a PRIVATE repo first (never public).
 
 from __future__ import annotations
 
-import os
-from pathlib import Path
 from typing import TYPE_CHECKING
 
+from lerobot.utils.constants import HF_LEROBOT_HOME
+
 if TYPE_CHECKING:
     from huggingface_hub import HfApi
 
@@ -39,12 +39,12 @@ def ensure_dataset_available(repo_id: str, *, api: HfApi, tags: list[str] | None
     if api.repo_exists(repo_id, repo_type="dataset"):
         return
 
-    cache_root = Path(os.environ.get("HF_LEROBOT_HOME", "~/.cache/huggingface/lerobot")).expanduser()
-    local_present = (cache_root / repo_id / "meta" / "info.json").is_file()
+    local_present = (HF_LEROBOT_HOME / repo_id / "meta" / "info.json").is_file()
     if not local_present:
         raise RuntimeError(
-            f"Dataset '{repo_id}' is neither on the Hub nor in the local cache "
-            f"({cache_root}). Record or download it first."
+            f"Dataset '{repo_id}' is not in the local cache ({HF_LEROBOT_HOME}) and could not be "
+            f"reached on the Hub — it may not exist, or be private and inaccessible with your "
+            f"token. Record or download it first, or run `hf auth login`."
         )
 
     print(f"[dataset] '{repo_id}' is local-only; pushing to a PRIVATE Hub repo...")

tests/jobs/test_dataset.py

@@ -42,7 +42,7 @@ def test_dataset_already_on_hub_is_noop():
 
 # Branch 2: not on Hub but present locally → always push privately.
 def test_dataset_local_only_uploads_privately(tmp_path, monkeypatch):
-    monkeypatch.setenv("HF_LEROBOT_HOME", str(tmp_path))
+    monkeypatch.setattr("lerobot.jobs.dataset.HF_LEROBOT_HOME", tmp_path)
     _make_local_cache(tmp_path, "user/ds")
 
     api = _api_with_dataset(False)
@@ -57,11 +57,11 @@ def test_dataset_local_only_uploads_privately(tmp_path, monkeypatch):
     mock_ds_cls.return_value.push_to_hub.assert_called_once_with(private=True, tags=["lerobot", "lelab"])
 
 
-# Branch 3: not on Hub, NOT in local cache → RuntimeError "neither".
+# Branch 3: not on Hub, NOT in local cache → RuntimeError.
 def test_dataset_neither_on_hub_nor_local_raises(tmp_path, monkeypatch):
-    monkeypatch.setenv("HF_LEROBOT_HOME", str(tmp_path))
+    monkeypatch.setattr("lerobot.jobs.dataset.HF_LEROBOT_HOME", tmp_path)
     # tmp_path is empty — no local cache.
 
     api = _api_with_dataset(False)
-    with pytest.raises(RuntimeError, match="neither"):
+    with pytest.raises(RuntimeError, match="not in the local cache"):
         ensure_dataset_available("user/ds", api=api)