message: In the overloaded HloVerifier::CheckShape, include the failing instruction in
  the error message.
diff: @@ -359,7 +359,10 @@ class ShapeVerifier : public DfsHloVisitor {
  Status CheckShape(const HloInstruction* instruction,
  const StatusOr<Shape>& expected_shape_status) {
  if (!expected_shape_status.ok()) {
  - return expected_shape_status.status();
  + Status s = expected_shape_status.status();
  + tensorflow::errors::AppendToMessage(&s, ", for instruction ",
  + instruction->ToString());
  + return s;
  }
  return CheckShape(instruction, expected_shape_status.ValueOrDie());
  }
  