Revert "Misleading exception raised during batch scaling (#1973)"

This reverts commit f8103f9.

Author: williamFalcon

pytorch_lightning/trainer/training_tricks.py

@@ -136,10 +136,7 @@ def scale_batch_size(self,
 
         """
         if not hasattr(model, batch_arg_name):
-            if not hasattr(model.hparams, batch_arg_name):
-                raise MisconfigurationException(
-                    'Neither of `model.batch_size` and `model.hparams.batch_size` found.'
-                )
+            raise MisconfigurationException(f'Field {batch_arg_name} not found in `model.hparams`')
 
         if hasattr(model.train_dataloader, 'patch_loader_code'):
             raise MisconfigurationException('The batch scaling feature cannot be used with dataloaders'
@@ -248,23 +245,17 @@ def _adjust_batch_size(trainer,
 
     """
     model = trainer.get_model()
-    if hasattr(model, batch_arg_name):
-        batch_size = getattr(model, batch_arg_name)
-    else:
-        batch_size = getattr(model.hparams, batch_arg_name)
+    batch_size = getattr(model, batch_arg_name)
     if value:
-        if hasattr(model, batch_arg_name):
-            setattr(model, batch_arg_name, value)
-        else:
-            setattr(model.hparams, batch_arg_name, value)        
+        setattr(model, batch_arg_name, value)
         new_size = value
         if desc:
             log.info(f'Batch size {batch_size} {desc}, trying batch size {new_size}')
     else:
         new_size = int(batch_size * factor)
         if desc:
             log.info(f'Batch size {batch_size} {desc}, trying batch size {new_size}')
-        setattr(model.hparams, batch_arg_name, new_size)
+        setattr(model, batch_arg_name, new_size)
     return new_size