Fixed the RoBERTa checkpoint conversion script according to the LM head refactoring.

pytorch_transformers/convert_roberta_checkpoint_to_pytorch.py

@@ -123,7 +123,7 @@ def convert_roberta_checkpoint_to_pytorch(roberta_checkpoint_path, pytorch_dump_
     model.lm_head.layer_norm.weight = roberta.model.decoder.lm_head.layer_norm.weight
     model.lm_head.layer_norm.bias = roberta.model.decoder.lm_head.layer_norm.bias
     model.lm_head.layer_norm.variance_epsilon = roberta.model.decoder.lm_head.layer_norm.eps
-    model.lm_head.weight = roberta.model.decoder.lm_head.weight
+    model.lm_head.decoder.weight = roberta.model.decoder.lm_head.weight
     model.lm_head.bias = roberta.model.decoder.lm_head.bias
 
     # Let's check that we get the same results.