Please Install pdftk in the environment.
If you are using Macbook, Please go to following link to download pdftk: https://www.pdflabs.com/tools/pdftk-the-pdf-toolkit/pdftk_server-2.02-mac_osx-10.11-setup.pkg
If you are using VM, Please install with the following command:
sudo apt-get install pdftk
Install Redis on Macbook Pro:
brew install redis
Before starting the app, you must start redis. In a separate terminal, run
redis-server