Ensure Yarn is part of the build chain - getting errors on yarn not installed on your system

[aaronlippold]

brew install yarn

https://yarnpkg.com/lang/en/docs/install/#mac-stable

Step 18/25 : RUN sh -c "RAILS_ENV=$RAILS_ENV RAILS_RELATIVE_URL_ROOT=$RAILS_RELATIVE_URL_ROOT SECRET_KEY_BASE=$(openssl rand -hex 64) bundle exec rake assets:precompile"
 ---> Running in 6dd6af3118f9
Yarn executable was not detected in the system.
Download Yarn at https://yarnpkg.com/en/docs/install
I, [2018-09-15T15:08:49.063520 #11]  INFO -- : Writing /var/www/heimdall/public/assets/FontAwesome-ecd72f31910a8ee2726fd17bd459be26f230779f3f3ed5f69ebf829e4b12e768.otf

[aaronlippold]

This may or may not be needed ...