Redmine

When I try to access Redmine 3.4-stable through passenger I end up with a web page that says :

Application error

Rails application failed to start properly

The Apache error log records these error messages:

/usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- bundler/setup (LoadError)
    from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /home/redmine/redmine/config/boot.rb:4:in `<top (required)>'
    from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /home/redmine/redmine/public/dispatch.fcgi:3:in `<main>'

The relevant line seems to be /home/redmine/redmine/config/boot.rb:4:in `<top (required)>'. The file contains:

# Set up gems listed in the Gemfile.
ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile', __FILE__)

require 'bundler/setup' if File.exists?(ENV['BUNDLE_GEMFILE'])

• Redmine 3.4-stable (as returned by git status)
• Fedora 27
• Apache: 2.4.33 (Fedora)
• Passenger-5.2.1
• Using postgresql 9.6.8
• Ruby 2.4.3 (2017-12-14) [x86_64-linux]

Redmine starts up when I use rails' web server bundle exec rails server webrick -e production.

Any help is welcomed