message: fix sess error
  This passed x.py check locally, not sure why it wasn't rebased right...
diff: @@ -74,7 +74,7 @@ pub(crate) fn get_vtable<'tcx>(
  } else {
  let vtable_alloc_id = match fx.tcx.vtable_allocation(ty, trait_ref) {
  Ok(alloc) => alloc,
  - Err(_) => fx.tcx.sess().fatal("allocation of constant vtable failed"),
  + Err(_) => fx.tcx.sess.fatal("allocation of constant vtable failed"),
  };
  let vtable_allocation = fx.tcx.global_alloc(vtable_alloc_id).unwrap_memory();
  let vtable_ptr = pointer_for_allocation(fx, vtable_allocation);
  