Fix type_check error message on evaluating bool expression
Fix type_check error message on evaluating bool expression

niboshi/chainer,niboshi/chainer,chainer/chainer,niboshi/chainer,okuta/chainer,okuta/chainer,okuta/chainer,chainer/chainer,chainer/chainer,chainer/chainer,hvy/chainer,wkentaro/chainer,niboshi/chainer,okuta/chainer,hvy/chainer,wkentaro/chainer,wkentaro/chainer,hvy/chainer,pfnet/chainer,hvy/chainer,wkentaro/chainer