The current Vagrantfile fails to build upon provisioning, as it lacks yarn.
Change the Vagrantfile to add the yarn repository, and install yarn.
cd /vagrant # This is where the host folder/repo is mounted
+# Add the yarn repo + yarn repo keys
+curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
+sudo apt-add-repository 'deb https://dl.yarnpkg.com/debian/ stable main'
+
# Add repo for Ruby 2.3 binaries
sudo apt-add-repository ppa:brightbox/ruby-ng
redis-tools \
postgresql \
postgresql-contrib \
+ yarn \
-y
# Set Ruby 2.3 as 'ruby'