`vuls prepare` doesn't work on Debian host due to apt-get confirmation prompt

[Code0x58]

vuls prepare won't actually install aptitude on a Debain host as it will get tripped up by a confirmation prompt.

This can be fixed by either adding DEBIAN_FRONTEND=noninteractive to the call environment, or simply adding a -y flag.

This is true for e40ef65 which is in the latest vuls/vuls Docker image.

[kotakanbe]

Thanks.
merged.

[Code0x58]

I realise that I went in completely the wrong direction as I didn't properly read the log output. Looking at it, I think the problem was that stdin wasn't available to read a response.

The -y is still needed to install packages though (unless all dependencies are met), so the path is still good.

I have make another issue to address what I actually encountered #260