If you see this:
Error: An unexpected error occurred during the `brew link` step
The formula built, but is not symlinked into /usr/local
Permission denied @ dir_s_mkdir - /usr/local/Frameworks
Error: Permission denied @ dir_s_mkdir - /usr/local/Frameworks
Do this:
sudo install -d -o $(whoami) -g admin /usr/local/Frameworks
Which is effectively:
sudo mkdir -p /usr/local/Frameworks
chown $(whoami):admin /usr/local/Frameworks