message: Improve error message when op_def to register does not match the currently registered op_def.
diff: @@ -32,7 +32,10 @@ def register_op_list(op_list):
  (op_list, type(op_list)))
  for op_def in op_list.op:
  if op_def.name in _registered_ops:
  - assert _registered_ops[op_def.name] == op_def
  + if _registered_ops[op_def.name] != op_def:
  + raise ValueError(
  + "Registered op_def for %s (%s) not equal to op_def to register (%s)"
  + % (op_def.name, _registered_ops[op_def.name], op_def))
  else:
  _registered_ops[op_def.name] = op_def
  