Fix metaworld_config.json not bundled in pip installs and AttributeError crash (#3017)

1. Include metaworld_config.json in package distributions by adding it to
   both MANIFEST.in (for sdist) and pyproject.toml package-data (for wheels).
   Without this, pip-installed lerobot raises FileNotFoundError when
   importing the metaworld environment.

2. Fix crash in sanity_check_dataset_name where the error message accesses
   policy_cfg.type when policy_cfg is None, raising AttributeError instead
   of the intended ValueError.

Fixes #2958

MANIFEST.in

@@ -1,2 +1,3 @@
 include src/lerobot/templates/lerobot_modelcard_template.md
 include src/lerobot/datasets/card_template.md
+include src/lerobot/envs/metaworld_config.json

pyproject.toml

@@ -214,6 +214,9 @@ lerobot-edit-dataset="lerobot.scripts.lerobot_edit_dataset:main"
 lerobot-setup-can="lerobot.scripts.lerobot_setup_can:main"
 
 # ---------------- Tool Configurations ----------------
+[tool.setuptools.package-data]
+lerobot = ["envs/*.json"]
+
 [tool.setuptools.packages.find]
 where = ["src"]
 

src/lerobot/utils/control_utils.py

@@ -189,7 +189,7 @@ def sanity_check_dataset_name(repo_id, policy_cfg):
     # Check if dataset_name starts with "eval_" but policy is missing
     if dataset_name.startswith("eval_") and policy_cfg is None:
         raise ValueError(
-            f"Your dataset name begins with 'eval_' ({dataset_name}), but no policy is provided ({policy_cfg.type})."
+            f"Your dataset name begins with 'eval_' ({dataset_name}), but no policy is provided."
         )
 
     # Check if dataset_name does not start with "eval_" but policy is provided