Where is Rails red development error page gone in Rails 6?

I am refactoring an application from Rails 5.2 to Rais 6.1. I created a new Rails 6 application, and move features from the old Rails 5.2 to the new Rails 6.1 application.

In development, the application starts correctly and produces html pasges. But when an error occurs, instead of showing classical error page with lots of information and parameters, it just displays the production error page stating that "We're sorry, but something went wrong".

I only modified the development.rb file to add action_mailer configuration:

Rails.application.configure do
  # Settings specified here will take precedence over those in config/application.rb.

  # In the development environment your application's code is reloaded on
  # every request. This slows down response time but is perfect for development
  # since you don't have to restart the web server when you make code changes.
  config.cache_classes = false

  # Do not eager load code on boot.
  config.eager_load = false

  # Show full error reports.
  config.consider_all_requests_local = true

  # Enable/disable caching. By default caching is disabled.
  # Run rails dev:cache to toggle caching.
  if Rails.root.join('tmp', 'caching-dev.txt').exist?
    config.action_controller.perform_caching = true
    config.action_controller.enable_fragment_cache_logging = true

    config.cache_store = :memory_store
    config.public_file_server.headers = {
      'Cache-Control' => "public, max-age=#{2.days.to_i}"
    }
  else
    config.action_controller.perform_caching = false

    config.cache_store = :null_store
  end

  # Store uploaded files on the local file system (see config/storage.yml for options).
  config.active_storage.service = :local

  # Print deprecation notices to the Rails logger.
  config.active_support.deprecation = :log

  # Raise an error on page load if there are pending migrations.
  config.active_record.migration_error = :page_load

  # Highlight code that triggered database queries in logs.
  config.active_record.verbose_query_logs = true

  # Debug mode disables concatenation and preprocessing of assets.
  # This option may cause significant delays in view rendering with a large
  # number of complex assets.
  config.assets.debug = true

  # Suppress logger output for asset requests.
  config.assets.quiet = true

  # Raises error for missing translations.
  # config.action_view.raise_on_missing_translations = true

  # Use an evented file watcher to asynchronously detect changes in source code,
  # routes, locales, etc. This feature depends on the listen gem.
  # config.file_watcher = ActiveSupport::EventedFileUpdateChecker

  # Define connection to email services
  config.action_mailer.default_url_options = { :host => 's721000108907b.odq.ch/' }
  config.action_mailer.delivery_method = :smtp
  config.action_mailer.perform_deliveries = false
  config.action_mailer.perform_caching = false
  config.action_mailer.raise_delivery_errors = true
  config.action_mailer.default :charset => "utf-8"
end

As all requests are already considered as local, how can I get the full error report I knew in Rails 5?

UPDATE: I applied upgrade recommendations to Rails 6.1, and identified an error message which probably relates to the issue. But I still don't undrestand it. Your help is welcome!

C:/Sites/DQ_Foundation/app/views/layouts/_header.html.erb:21: warning: __FILE__ in eval may not return location in binding; use Binding#source_location instead
C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/web-console-3.7.0/lib/web_console/exception_mapper.rb:31: warning: in `eval'

ArgumentError: wrong number of arguments (given 2, expected 3)

Thanks a lot!