Fix flake8 errors
Fix flake8 errors

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