Rails 6 drops support for PostgreSQL version less than 9.3

Before Rails 6, Rails was supporting PostgreSQL from version 9.1 and above. But in Rails 6, support for versions less than 9.3 is dropped. If your PostgreSQL version is less than 9.3 then an error is shown as follows.

Your version of PostgreSQL (90224) is too old. Active Record supports PostgreSQL >= 9.3.

Travis CI uses PostgreSQL 9.2 by default in their images. So this error can occur while testing the app on Travis CI with Rails 6. It can be resolved by using an addon for PostgreSQL.