Error on multi_tenancy require when using 'rails runner'

[Mikkel Kirkgaard Nielsen]

I'm migrating a Redmine installation from Ubuntu 14.04 with a custom Redmine setup (directly from svn repository) to Ubuntu 16.04 trying to use the pre-packaged redmine. The sparse documentation of the Debian/Ubuntu multi tenancy/instance feature has given me some headache on the journey but inspecting the source to decipher what should go where while learning a little ruby I've succeeded getting the web application running.

However something basic in the initialization of the rails environment fails when trying to use "rails runner" for calling into the application from the command line.
My specific use is calling Repository.fetch_changesets() for updating references between code and tickets (as pr. http://www.redmine.org/projects/redmine/wiki/RedmineSettings#Fetch-commits-automatically). But independent of the Ruby code that is going to be executed the loading of the file lib/redmine/multi_tenancy.rb from config/multitenancy_environment.rb fails. Here's the full output;

# /usr/share/redmine/bin/rails runner --environment=production Repository.fetch_changesets
/usr/share/redmine/config/application.rb:79:in `instance_eval': cannot load such file -- redmine/multi_tenancy (LoadError)
        from /var/lib/gems/2.3.0/gems/polyglot-0.3.5/lib/polyglot.rb:65:in `require'
        from /usr/lib/ruby/vendor_ruby/active_support/dependencies.rb:274:in `block in require'
        from /usr/lib/ruby/vendor_ruby/active_support/dependencies.rb:240:in `load_dependency'
        from /usr/lib/ruby/vendor_ruby/active_support/dependencies.rb:274:in `require'
        from (eval):19:in `<class:Application>'
        from /usr/share/redmine/config/application.rb:79:in `instance_eval'
        from /usr/share/redmine/config/application.rb:79:in `<class:Application>'
        from /usr/share/redmine/config/application.rb:8:in `<module:RedmineApp>'
        from /usr/share/redmine/config/application.rb:7:in `<top (required)>'
        from /usr/lib/ruby/vendor_ruby/rails/commands/runner.rb:51:in `require'
        from /usr/lib/ruby/vendor_ruby/rails/commands/runner.rb:51:in `<top (required)>'
        from /usr/lib/ruby/vendor_ruby/rails/commands/commands_tasks.rb:123:in `require'
        from /usr/lib/ruby/vendor_ruby/rails/commands/commands_tasks.rb:123:in `require_command!'
        from /usr/lib/ruby/vendor_ruby/rails/commands/commands_tasks.rb:90:in `runner'
        from /usr/lib/ruby/vendor_ruby/rails/commands/commands_tasks.rb:39:in `run_command!'
        from /usr/lib/ruby/vendor_ruby/rails/commands.rb:17:in `<top (required)>'
        from /usr/share/redmine/bin/rails:4:in `require'
        from /usr/share/redmine/bin/rails:4:in `<main>'

I'm not well versed in Ruby nor Rails but it seems like there is something in the multi tenancy setup that has not being setup correctly for "rails runner" to be able to function correctly.

# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04.2 LTS
Release: 16.04
Codename: xenial

# apt-cache policy redmine
redmine:
  Installed: 3.2.1-2
  Candidate: 3.2.1-2
  Version table:
 *** 3.2.1-2 500
        500 http://dk.archive.ubuntu.com/ubuntu xenial/universe amd64 Packages
        500 http://dk.archive.ubuntu.com/ubuntu xenial/universe i386 Packages
        100 /var/lib/dpkg/status