Do not treat OSErrors as expected about fusepy HOT 4 CLOSED

Actually older revisions used exactly the design you propose. I finally decided 
to use OSError because it 
simplified a lot many kinds of wrapper filesystems and it allows you to reuse 
existing code. For example you can 
see that loopback.py can use directly some of the functions in os. There is 
indeed the drawback of overloading 
OSError however.

I personally prefer the way it is now, but I realize the subject is debatable 
and would consider switching back to 
a FUSEError scheme if there is demand. However I'm not going to break 
compatibility again just for this.

I see. Would you consider making _operation_wrapper a method of the FUSE class, 
so
that one can change the behaviour by subclassing?

Yes, this is a good suggestion.

Fixed in rev. 17