I don't see how you can make an integer equal what the method is supposed to do - namely copy a file from a source to a destination and either overwrite or not. I do not recall ever reading that the method provides a return value.
This would be the first time I have ever seen it declared that an error is raised and provides only a number and no text message. Apparently the number is about trying to modify a write protected file.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.