[model.from_pretrained] raise exception early on failed load (#12574)

* [model.from_pretrained] raise exception early on failed load

Currently if `load` pretrained weights fails in `from_pretrained`, we first print a whole bunch of successful messages and then fail - this PR puts the exception first to avoid all the misleading messages.

* style
Co-authored-by: Suraj Patil <surajp815@gmail.com>

src/transformers/modeling_utils.py

@@ -1431,6 +1431,10 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin, GenerationMixin, PushToHubMix
 
         load(model_to_load, prefix=start_prefix)
 
+        if len(error_msgs) > 0:
+            error_msg = "\n\t".join(error_msgs)
+            raise RuntimeError(f"Error(s) in loading state_dict for {model.__class__.__name__}:\n\t{error_msg}")
+
         if len(unexpected_keys) > 0:
             logger.warning(
                 f"Some weights of the model checkpoint at {pretrained_model_name_or_path} were not used when "
@@ -1454,9 +1458,6 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin, GenerationMixin, PushToHubMix
                 f"If your task is similar to the task the model of the checkpoint was trained on, "
                 f"you can already use {model.__class__.__name__} for predictions without further training."
             )
-        if len(error_msgs) > 0:
-            error_msg = "\n\t".join(error_msgs)
-            raise RuntimeError(f"Error(s) in loading state_dict for {model.__class__.__name__}:\n\t{error_msg}")
 
         return model, missing_keys, unexpected_keys, error_msgs