fixing PYTORCH_PRETRAINED_BERT_CACHE use in examples

examples/run_swag.py

@@ -367,7 +367,7 @@ def main():
 
     # Prepare model
     model = BertForMultipleChoice.from_pretrained(args.bert_model,
-        cache_dir=os.path.join(PYTORCH_PRETRAINED_BERT_CACHE, 'distributed_{}'.format(args.local_rank)),
+        cache_dir=os.path.join(str(PYTORCH_PRETRAINED_BERT_CACHE), 'distributed_{}'.format(args.local_rank)),
         num_choices=4)
     if args.fp16:
         model.half()