message: [XLA] Return an error for xla::Cholesky() for complex types.
  This is better than returning the wrong answer, as we do at the moment.
diff: @@ -26,6 +26,7 @@ limitations under the License.
  #include "tensorflow/compiler/xla/client/lib/triangular_solve.h"
  #include "tensorflow/compiler/xla/client/xla_builder.h"
  #include "tensorflow/compiler/xla/literal.h"
  +#include "tensorflow/compiler/xla/primitive_util.h"
  #include "tensorflow/compiler/xla/shape_util.h"
  #include "tensorflow/compiler/xla/status_macros.h"
  #include "tensorflow/compiler/xla/statusor.h"
  @@ -158,6 +159,12 @@ XlaOp Cholesky(XlaOp a, int64 block_size,
  ShapeUtil::HumanString(a_shape));
  }
  + if (primitive_util::IsComplexType(a_shape.element_type())) {
  + return Unimplemented(
  + "Complex types are not implemented in Cholesky; got shape %s",
  + ShapeUtil::HumanString(a_shape));
  + }
  +
  if (block_size < 1) {
  return InvalidArgument(
  "block_size argument to Cholesky must be >= 1; got %d", block_size);
  