eloiim:~ iivri.andre$ brew install eris docker-machine virtualbox
Updating Homebrew...
==> Auto-updated Homebrew!
Updated 1 tap (homebrew/core).
==> Updated Formulae
megatools
Error: No available formula with the name "virtualbox"
==> Searching for similarly named formulae...
Error: No similarly named formulae found.
==> Searching taps...
These formulae were found in taps:
Caskroom/cask/virtualbox-extension-pack
Caskroom/cask/virtualbox
Caskroom/versions/virtualbox-beta
Caskroom/versions/virtualbox-extension-pack-beta
To install one of them, run (for example):
brew install Caskroom/cask/virtualbox-extension-pack
THIS is the error I am getting when trying to install eris. How do I fix this ?