> The test makes sure that the error message contains the path to the
> file (which the incomplete error message you report also does, BTW),
> and an explanation of the error (to address the OP’s concern that the
> message must be helpful): it looks for the string 'denied'; if this is
> not cross-platform, I won’t commit this line. 

I really don't think C error messages are portable, so you shouldn't
test for them :)