Why I am getting Could not find multi_json-1.3.1 in any of the sources?

Question

I have a simple Rails application I want to deploy to Heroku. When I run the below command

git push heroku master

The below error message is di

Answer 1

I have solved it by the following steps.

Removed Gemfile.lock
bundle install

The cause of the problem is initially my Gemfile.lock has multi_json-1.3.1

Now it has the version multi_json-1.3.2