Add uint8 specialization in error message construction
Add uint8 specialization in error message construction

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