message: fix Stderr::as_file_handle error message
diff: @@ -102,7 +102,7 @@ impl FileDescriptor for io::Stdout {
  impl FileDescriptor for io::Stderr {
  fn as_file_handle<'tcx>(&self) -> InterpResult<'tcx, &FileHandle> {
  - throw_unsup_format!("stdout cannot be used as FileHandle");
  + throw_unsup_format!("stderr cannot be used as FileHandle");
  }
  fn read<'tcx>(&mut self, _communicate_allowed: bool, _bytes: &mut [u8]) -> InterpResult<'tcx, io::Result<usize>> {
  