use mkstemp instead of TemporaryDirectory for python 2.7
use mkstemp instead of TemporaryDirectory for python 2.7

keisuke-umezawa/chainer,niboshi/chainer,chainer/chainer,pfnet/chainer,hvy/chainer,wkentaro/chainer,cupy/cupy,chainer/chainer,ronekko/chainer,hvy/chainer,niboshi/chainer,okuta/chainer,rezoo/chainer,jnishi/chainer,wkentaro/chainer,jnishi/chainer,ktnyt/chainer,keisuke-umezawa/chainer,cupy/cupy,hvy/chainer,keisuke-umezawa/chainer,niboshi/chainer,ktnyt/chainer,jnishi/chainer,ktnyt/chainer,cupy/cupy,kiyukuta/chainer,anaruse/chainer,chainer/chainer,wkentaro/chainer,delta2323/chainer,niboshi/chainer,jnishi/chainer,cupy/cupy,aonotas/chainer,ktnyt/chainer,okuta/chainer,kashif/chainer,chainer/chainer,okuta/chainer,hvy/chainer,tkerola/chainer,keisuke-umezawa/chainer,ysekky/chainer,okuta/chainer,wkentaro/chainer