message: Make the definition of summary operations a warning instead of raising an exception.
diff: @@ -29,6 +29,7 @@ from tensorflow.python.framework import ops
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import control_flow_ops
  from tensorflow.python.ops import variable_scope
  +from tensorflow.python.platform import tf_logging as logging
  _SUMMARY_OPS = ("ScalarSummary",)
  @@ -111,7 +112,8 @@ class TPUReplicateContext(control_flow_ops.ControlFlowContext):
  raise ValueError("Placeholder %s is not supported." % op.name)
  if op.type in _SUMMARY_OPS:
  - raise ValueError("Summary operations are not currently supported.")
  + logging.warning(
  + "Summary operations are not currently supported (%s)" % op.name)
  if any(x.dtype._is_ref_dtype for x in op.inputs):
  raise NotImplementedError(
  