Scenario 1.1. Signup
1.1.F2. Sign up fails when username already exists.
GIVENuser visit signup page

WHENuser type "admin" into input "username"ANDuser type "admin2@example.com" into input "email"ANDuser type "admin1234" into input "password"ANDuser type "admin1234" into input "confirm-password"ANDuser click button "sign-up"THENuser see "The username field already exists"
