Chapters 7 to 8 - Loss of "Create My Account" button

[Howard Gilbert]

I am completely new to Rails and have started working through the online version of Ruby on Rails Tutorial (Rails 5).   I am currently baffled and
hope someone may be able to suggest something to help

At the end of Chapter 7 I had the "Create My Account" button working both with valid and invalid input data.

This no longer works in Chapter 8. Giving the message: "ROUTING ERROR  No route matches [POST] "/signup"".

Routes listed on the Error Page include "POST  /login(.:format) sessions#create"  I assume this POST stems from "resources :users" in routes.rb but I cannot fathom
why it has ceased to work in the new Chapter. 

If I add "post '/signup'",  to: "users#create" into routes.rb it is back to working   fine.

Thank you in anticipation.