Rails upgrade from 5.0 to 5.1 - Cannot start webrick [duplicate] - ruby-on-rails

Question

Before writing this question I looked at these answers, but was unable to find a solution.:
Error when execute rails generate scaffold User name:string email:string
rake aborted! undefined method `migration_error=' for ActiveRecord::Base:Class
Error launching Rails server: undefined method 'configure'
When I try to start a new application (for Hartl's tutorial, Chapter 2), at the stage scaffold start, I got an error like:
**undefined method `configure' for #<SampleApp2::Application:0x00000101a74610> (NoMethodError)**
But thanks to the above examples, I edited the development.rb file:
DemoApp::Application.configure do
(Yes, my application is called demo_app so I transformed its name).
After that, I tried to run scaffold again but got a new error:
**method_missing': undefined method raise_in_transactional_callbacks=' for ActiveRecord::Base:Class (NoMethodError)**
In response to similar cases indicates a migration method - that it should be removed from the file development.rb. Similarly, I tried to find in this file raise_in_transactional_callbacks method, but it's not there!
In addition, I would say that the full code that produces in cmd is very large:
C:\Sites\demo_app>rails generate scaffold User name:string email:string
invoke active_record
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/active_record/dynamic_matchers.rb:22:in `method_missing': undefined method `raise_in_transactional_callbacks=' for ActiveRecord::Base:Class (NoMethodError)
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/active_record/railtie.rb:166:in `block (3 levels) in <class:Railtie>'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/active_record/railtie.rb:165:in `each'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/active_record/railtie.rb:165:in `block (2 levels) in <class:Railtie>'
…
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/railties-4.0.2/lib/rails/commands.rb:48:in `<top (required)>'
from bin/rails:4:in `require'
from bin/rails:4:in `<main>'
Where the ...(ellipsis) - specially cut similar code.
That's all. I would be grateful for any help!

Answer 1

Your config/application.rb has the following line:
config.active_record.raise_in_transactional_callbacks = true
This is not a valid configuration value in your version of Rails. You will need to delete it or comment it out to continue.
Note: this error and the one that preceded it are indicative of an incomplete Rails version change. If you are in the early stages of a tutorial, you might seriously consider restarting your application using your preferred version of Rails from the very start. This will help you avoid this type of error until you are more familiar with the technology.

Answer 2

I had the same issue when upgrading an app from Rails 5.0.1 to Rails 5.1.0.beta1.
When starting the server (rails s), I got the following error message:
/home/user01/.rvm/gems/ruby-2.4.0#global/gems/activerecord-5.1.0.beta1/lib/active_record/dynamic_matchers.rb:22:in `method_missing': undefined method `raise_in_transactional_callbacks=' for ActiveRecord::Base:Class (NoMethodError)
Same ills, same cures.
Commenting out the following line, in config/application.rb, solved the issue...
config.active_record.raise_in_transactional_callbacks = true
After some investigation, I found that this line was default in Rails 4.2.1, vanished in Rails 5.0.0, and now raises an error in Rails 5.1.0.beta1...

Answer 3

If you don't see config.active_record.raise_in_transactional_callbacks = true in config/application.rb it might exist in your environment configs. For my app it was being set it in config/environments/development.rb and config/environments/test.rb