Fix to test against new chainerx.GradientError
Fix to test against new chainerx.GradientError

keisuke-umezawa/chainer,wkentaro/chainer,hvy/chainer,niboshi/chainer,jnishi/chainer,chainer/chainer,ktnyt/chainer,hvy/chainer,niboshi/chainer,jnishi/chainer,niboshi/chainer,tkerola/chainer,hvy/chainer,niboshi/chainer,okuta/chainer,jnishi/chainer,hvy/chainer,keisuke-umezawa/chainer,keisuke-umezawa/chainer,wkentaro/chainer,chainer/chainer,ktnyt/chainer,keisuke-umezawa/chainer,wkentaro/chainer,wkentaro/chainer,okuta/chainer,pfnet/chainer,jnishi/chainer,chainer/chainer,okuta/chainer,chainer/chainer,ktnyt/chainer,okuta/chainer,ktnyt/chainer