message: Use array_ops.where_v2 in _SelectGradV2
  The usages of array_ops.where_v2 and array_ops.where
  are the same as else and then are None in both cases.
  Use array_ops.where_v2 for consistency.
diff: @@ -1321,7 +1321,7 @@ def _SelectGradV2(op, grad):
  # Reduce away broadcasted leading dims.
  gx = math_ops.reduce_sum(gx, axis=math_ops.range(rankdiff_x))
  # Reduce but keep x's 1-valued dims which were broadcast.
  - axis = array_ops.where(gx_shape[rankdiff_x:] > x_shape)
  + axis = array_ops.where_v2(gx_shape[rankdiff_x:] > x_shape)
  # tf.where returns 2D so squeeze.
  axis = array_ops.squeeze(axis)
  gx = math_ops.reduce_sum(gx, keepdims=True, axis=axis)
  @@ -1333,7 +1333,7 @@ def _SelectGradV2(op, grad):
  # Reduce away broadcasted leading dims.
  gy = math_ops.reduce_sum(gy, axis=math_ops.range(rankdiff_y))
  # Reduce but keep y's 1-valued dims which were broadcast.
  - axis = array_ops.where(gy_shape[rankdiff_y:] > y_shape)
  + axis = array_ops.where_v2(gy_shape[rankdiff_y:] > y_shape)
  # tf.where returns 2D so squeeze.
  axis = array_ops.squeeze(axis)
  gy = math_ops.reduce_sum(gy, keepdims=True, axis=axis)
  