Install python-apt in the base image

aux/post-install.sh

@@ -15,7 +15,7 @@ SSH_KEY="ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEA6NF8iallvQVp22WDkTkyrtvp9eWW6A8YVr+
 # Also set up a 'vagrant' user for easy Vagrant compatibility.
 
 chroot $TARGET apt-get install -y \
-       openssh-server sudo ca-certificates python
+       openssh-server sudo ca-certificates python python-apt
 
 mkdir -p $TARGET/root/.ssh
 echo "$SSH_KEY" \