Recent vagrant breaks build (OSX 10.11)

[rossjones]

On a recent vagrant on OSX 10.11 the build is broken when you vagrant up complaining about the network, with the following error

 Vagrant attempted to execute the capability 'configure_networks'
on the detect guest OS 'linux', but the guest doesn't
support that capability. This capability is required for your
configuration of Vagrant. Please either reconfigure Vagrant to
avoid this capability or fix the issue by creating the capability

This is because there needs to be a file called /etc/os-release with the following contents:

NAME="Ubuntu"
VERSION="12.04 LTS, Precise Pangolin"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu precise (12.04 LTS)"
VERSION_ID="12.04"