Redmine

Trying upgrade with this environment

ruby -v
ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-linux-gnu]

rails -v
Rails 6.1.7

gem -v
2.7.6

Leads to the following error when installing gems

Fetching gem metadata from https://rubygems.org/..
Resolving dependencies.........
Using rake 13.0.6
Using concurrent-ruby 1.2.2
Using i18n 1.10.0
Fetching minitest 5.18.0
Installing minitest 5.18.0
Gem::RuntimeRequirementNotMetError: minitest requires Ruby version < 4.0, >= 2.6. The current ruby version is 2.5.0.
An error occurred while installing minitest (5.18.0), and Bundler cannot continue.
<pre>
Make sure that `gem install minitest -v '5.18.0' --source 'https://rubygems.org/'` succeeds before bundling.
</pre>

In Gemfile:
  rails was resolved to 6.1.7.2, which depends on
    actioncable was resolved to 6.1.7.2, which depends on
      actionpack was resolved to 6.1.7.2, which depends on
        actionview was resolved to 6.1.7.2, which depends on
          rails-dom-testing was resolved to 2.0.3, which depends on
            activesupport was resolved to 6.1.7.2, which depends on
              minitest