Fix error type for Python 2
Fix error type for Python 2

okuta/chainer,keisuke-umezawa/chainer,ktnyt/chainer,ktnyt/chainer,hvy/chainer,chainer/chainer,wkentaro/chainer,hvy/chainer,jnishi/chainer,okuta/chainer,wkentaro/chainer,jnishi/chainer,hvy/chainer,keisuke-umezawa/chainer,keisuke-umezawa/chainer,wkentaro/chainer,hvy/chainer,jnishi/chainer,chainer/chainer,okuta/chainer,rezoo/chainer,okuta/chainer,ktnyt/chainer,ronekko/chainer,ktnyt/chainer,pfnet/chainer,niboshi/chainer,aonotas/chainer,jnishi/chainer,niboshi/chainer,keisuke-umezawa/chainer,niboshi/chainer,anaruse/chainer,chainer/chainer,tkerola/chainer,wkentaro/chainer,chainer/chainer,niboshi/chainer