Hello-world.evil confinement

I was trying out the hello-world snap on my os/kernel and got this:

Hello Evil World!
This example demonstrates the app confinement
You should see a permission denied error next
If you see this line the confinement is not working correctly, please file a bug

I am using ubuntu 16.04 with a custom 4.14 kernel for my hardware. I already custom built the kernel to include missing features to get app armor to work (specifically squashfs compression) but perhaps there are more requirements for confinement to work correctly? If so, is this documented any where?

See https://github.com/snapcore/sample-kernels/tree/master