_mapErrnoToPathError

private fn

Exception _mapErrnoToPathError(string op,  string p,  int  err,  Throwable next,
       string file =  __FILE__,  size_t line =  __LINE__)

Map an errno value to the PathError hierarchy.

`op`	Operation name for the message.
`p`	Path the operation was attempted on.
`err`	errno (or Windows error code) to map.
`next`	Optional chained cause.
`file`	Reported source file of the failure site.
`line`	Reported source line of the failure site.

A NotFoundError, PermissionError, or PathError describing err.