Adding custom github webhook getting "NameError: uninitialized constant Handlers"

Hello,

Newbie Ruby developer, I am trying to add a custom github webhook listener to shipit. I have modified by environments/development.rb and added the following lines

Shipit::Webhooks.register_handler('issue_comment') do |params| puts "Webhook Calling issue_comment" end

I end up with the following error message on start

rake aborted! NameError: uninitialized constant Handlers /usr/local/bundle/gems/shipit-engine-0.31.0/app/models/shipit/webhooks.rb:6:in default_handlers'
/usr/local/bundle/gems/shipit-engine-0.31.0/app/models/shipit/webhooks.rb:18:in reset_handlers!' /usr/local/bundle/gems/shipit-engine-0.31.0/app/models/shipit/webhooks.rb:14:in handlers'
/usr/local/bundle/gems/shipit-engine-0.31.0/app/models/shipit/webhooks.rb:22:in register_handler' /var/shipit/config/environments/development.rb:65:in block in <top (required)>'
/usr/local/bundle/gems/railties-6.0.2.1/lib/rails/railtie.rb:216:in instance_eval' /usr/local/bundle/gems/railties-6.0.2.1/lib/rails/railtie.rb:216:in configure'
/var/shipit/config/environments/development.rb:1:in <top (required)>' /usr/local/bundle/gems/railties-6.0.2.1/lib/rails/engine.rb:612:in block (2 levels) in class:Engine'
/usr/local/bundle/gems/railties-6.0.2.1/lib/rails/engine.rb:611:in each' /usr/local/bundle/gems/railties-6.0.2.1/lib/rails/engine.rb:611:in block in class:Engine'
/usr/local/bundle/gems/railties-6.0.2.1/lib/rails/initializable.rb:32:in instance_exec' /usr/local/bundle/gems/railties-6.0.2.1/lib/rails/initializable.rb:32:in run'
/usr/local/bundle/gems/railties-6.0.2.1/lib/rails/initializable.rb:61:in block in run_initializers' /usr/local/bundle/gems/railties-6.0.2.1/lib/rails/initializable.rb:50:in each'
/usr/local/bundle/gems/railties-6.0.2.1/lib/rails/initializable.rb:50:in tsort_each_child' /usr/local/bundle/gems/railties-6.0.2.1/lib/rails/initializable.rb:60:in run_initializers'
/usr/local/bundle/gems/railties-6.0.2.1/lib/rails/application.rb:363:in initialize!' /var/shipit/config/environment.rb:5:in <top (required)>'
/usr/local/bundle/gems/railties-6.0.2.1/lib/rails/application.rb:339:in require_environment!' /usr/local/bundle/gems/railties-6.0.2.1/lib/rails/application.rb:515:in block in run_tasks_blocks'
Tasks: TOP => railties:install:migrations => db:load_config => environment
(See full trace by running task with --trace)
`
Any assistance would be greatly appreciated.

Start with app/models/shipit/webhooks.rb, especially default_handlers, reset_handlers!, handlers, and register_handler, then compare its initialization with config/environments/development.rb. Reproduce the startup failure and trace why the custom registration reaches the uninitialized Handlers constant; done means the environment initializes and the custom issue_comment handler can be registered without the NameError.