_rethrowMapped

private fn

void _rethrowMapped(string op,  string p,  Throwable ex,
       string file =  __FILE__,  size_t line =  __LINE__)

Re-throw a filesystem exception mapped into the PathError hierarchy.

`op`	Operation name for the message.
`p`	Path the operation was attempted on.
`ex`	Original exception carrying an errno/Windows error code.
`file`	Reported source file of the failure site.
`line`	Reported source line of the failure site.

NotFoundError, PermissionError, or PathError wrapping ex.