Sorry, you can’t use byebug without Readline, Homebrew update error for macOS Sierra

One day suddenly I started seeing a weird issue inside my Rails application.

Last night it was working fine, the next day I was wondering why I am not able to boot my Rails application. I was curious that what happens overnight.

I was not aware of doing anything special with adding new ruby dependencies or updating anything related to existing one.

Sorry, you can't use byebug without Readline To solve this, you need to rebuild Ruby with Readline support.
If using Ubuntu, try

sudo apt-get install libreadline-dev

# then reinstall your Ruby
rvm reinstall ruby-2.3.1

bin/rails:6: warning: already initialized constant APP_PATH

/Users/rakesh/projects/workforce/bin/rails:6: warning: previous definition of APP_PATH was here

After recalling my past activity I got to know what could be the potential cause behind this 😃

Last night I had updated the Homebrew to Homebrew 1.1.1-13-gd536070. It was causing the problem and blocking the Rails application.

Here are the simplest solutions 😍

You need to add the development dependency rb-readline but adding this tends to lead to a couple of development issues you can look here issuecomment-138492675 for more details.

# in your Gemfile

group :development do 
  gem 'rb-readline'
end

Just reinstall the ruby version and It should work as before.

# reinstall ruby
rvm reinstall ruby-2.3.1

I hope it will help somebody, somewhere ☺️