Add back case return_value_policy::_return_as_bytes

Author: rwgk

include/pybind11/eigen/matrix.h

@@ -360,6 +360,9 @@ struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
                 return eigen_ref_array<props>(*src);
             case return_value_policy::reference_internal:
                 return eigen_ref_array<props>(*src, parent);
+            case return_value_policy::_return_as_bytes:
+                pybind11_fail("return_value_policy::_return_as_bytes does not apply.");
+                break;
             default:
                 throw cast_error("unhandled return_value_policy: should not happen!");
         };

include/pybind11/eigen/tensor.h

@@ -316,6 +316,10 @@ struct type_caster<Type, typename eigen_tensor_helper<Type>::ValidType> {
                 writeable = !std::is_const<C>::value;
                 break;
 
+            case return_value_policy::_return_as_bytes:
+                pybind11_fail("return_value_policy::_return_as_bytes does not apply.");
+                break;
+
             default:
                 pybind11_fail("pybind11 bug in eigen.h, please file a bug report");
         }