fix: Added dedicated error handling to load and get_model_path (#775)

* fix: Added dedicated error handling to load and get_model_path

Added proper error handling to load and get_model_path by adding a dedicated exception class, because when the local path is not right, it still throws the huggingface RepositoryNotFoundError

* fix: Changed error message and resolved lack of import

* fix: Removed redundant try-catch block

* nits in message

* nits in message

---------

Co-authored-by: Awni Hannun <awni@apple.com>

llms/mlx_lm/utils.py

@@ -14,6 +14,7 @@ from typing import Any, Callable, Dict, Generator, Optional, Tuple, Union
 import mlx.core as mx
 import mlx.nn as nn
 from huggingface_hub import snapshot_download
+from huggingface_hub.utils._errors import RepositoryNotFoundError
 from mlx.utils import tree_flatten
 from transformers import AutoTokenizer, PreTrainedTokenizer
 
@@ -33,6 +34,12 @@ MODEL_REMAPPING = {
 MAX_FILE_SIZE_GB = 5
 
 
+class ModelNotFoundError(Exception):
+    def __init__(self, message):
+        self.message = message
+        super().__init__(self.message)
+
+
 def _get_classes(config: dict):
     """
     Retrieve the model and model args classes based on the configuration.
@@ -69,20 +76,29 @@ def get_model_path(path_or_hf_repo: str, revision: Optional[str] = None) -> Path
     """
     model_path = Path(path_or_hf_repo)
     if not model_path.exists():
-        model_path = Path(
-            snapshot_download(
-                repo_id=path_or_hf_repo,
-                revision=revision,
-                allow_patterns=[
-                    "*.json",
-                    "*.safetensors",
-                    "*.py",
-                    "tokenizer.model",
-                    "*.tiktoken",
-                    "*.txt",
-                ],
+        try:
+            model_path = Path(
+                snapshot_download(
+                    repo_id=path_or_hf_repo,
+                    revision=revision,
+                    allow_patterns=[
+                        "*.json",
+                        "*.safetensors",
+                        "*.py",
+                        "tokenizer.model",
+                        "*.tiktoken",
+                        "*.txt",
+                    ],
+                )
             )
-        )
+        except RepositoryNotFoundError:
+            raise ModelNotFoundError(
+                f"Model not found for path or HF repo: {path_or_hf_repo}.\n"
+                "Please make sure you specified the local path or Hugging Face"
+                " repo id correctly.\nIf you are trying to access a private or"
+                " gated Hugging Face repo, make sure you are authenticated:\n"
+                "https://huggingface.co/docs/huggingface_hub/en/guides/cli#huggingface-cli-login"
+            ) from None
     return model_path