Whenever I start the server and go to localhost:3000, this error shows up. I've already allowed the firewall settings in my mac, but this error just keeps showing up.
This same thing happens when I tried installing and running on my friend's laptop.
HERE IS THE SCREENSHOT OF THE ERROR link to the screenshot
According to your screenshot. I tells that you don't have a database scheduler_development. To resolve this, run:
rake db:create
rake db:migrate