missing self. in weights_filename_local (#79)

line 218 when the weight is somehow not loaded correctly
we get an error on weights_filename_local is not defined instead of the real error
which is because it should be self.weights_filename_local instead of weights_filename_local

torchxrayvision/models.py

@@ -215,7 +215,7 @@ def __init__(self,
 
                 self.load_state_dict(savedmodel.state_dict())
             except Exception as e:
-                print("Loading failure. Check weights file:", weights_filename_local)
+                print("Loading failure. Check weights file:", self.weights_filename_local)
                 raise e
 
             self.eval()