Use Thor's self.exit_on_failure? to exit whenever accessing the generators from the CLI and a Thor::Error is raised.

railties/lib/rails/commands/application.rb

@@ -15,4 +15,16 @@ require 'rubygems' if ARGV.include?("--dev")
 require 'rails/generators'
 require 'rails/generators/rails/app/app_generator'
 
+module Rails
+  module Generators
+    class AppGenerator
+      # We want to exit on failure to be kind to other libraries
+      # This is only when accessing via CLI
+      def self.exit_on_failure?
+        true
+      end
+    end
+  end
+end
+
 Rails::Generators::AppGenerator.start