Trying to bring an old install up to date

I'm attempting to bring up an installation from 10.6.3 to current release. I was able to incrementally change image versions up to 10.7.4. Beyond that, with 10.8.0, the db migration starts to fail:

Migrating database...
rake aborted!
NoMethodError: undefined method config' for Gitlab:Module /home/git/gitlab/lib/gitlab/shell.rb:353:in gitlab_shell_path'
/home/git/gitlab/lib/gitlab/shell.rb:333:in version' /home/git/gitlab/config/initializers/5_backend.rb:3:in <top (required)>'
/home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:268:in load' /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:268:in block in load'
/home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:240:in load_dependency' /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:268:in load'
Migrating database...
rake aborted!
NoMethodError: undefined method config' for Gitlab:Module /home/git/gitlab/lib/gitlab/shell.rb:353:in gitlab_shell_path'
/home/git/gitlab/lib/gitlab/shell.rb:333:in version' /home/git/gitlab/config/initializers/5_backend.rb:3:in <top (required)>'
/home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:268:in load' /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/railties-4.2.10/lib/rails/engine.rb:652:in block in load_config_initializer'
/home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/activesupport-4.2.10/lib/active_support/notifications.rb:166:in instrument' /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/railties-4.2.10/lib/rails/engine.rb:651:in load_config_initializer'
postgresql:
/home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/railties-4.2.10/lib/rails/engine.rb:616:in block (2 levels) in <class:Engine>' /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/railties-4.2.10/lib/rails/engine.rb:615:in each'
/home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/railties-4.2.10/lib/rails/engine.rb:615:in block in <class:Engine>' /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/railties-4.2.10/lib/rails/initializable.rb:30:in instance_exec'
/home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/railties-4.2.10/lib/rails/initializable.rb:30:in run' /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/railties-4.2.10/lib/rails/initializable.rb:55:in block in run_initializers'
/home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/railties-4.2.10/lib/rails/initializable.rb:44:in each' /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/railties-4.2.10/lib/rails/initializable.rb:44:in tsort_each_child'
/home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/railties-4.2.10/lib/rails/initializable.rb:54:in run_initializers' /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/railties-4.2.10/lib/rails/application.rb:352:in initialize!'
/home/git/gitlab/config/environment.rb:11:in <top (required)>' /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:274:in require'
/home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:274:in block in require' /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:240:in load_dependency'
/home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:274:in require' /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/railties-4.2.10/lib/rails/application.rb:328:in require_environment!'
/home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/railties-4.2.10/lib/rails/application.rb:457:in block in run_tasks_blocks' /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/rake-12.3.1/exe/rake:27:in <top (required)>'
Tasks: TOP => db:migrate => environment
(See full trace by running task with --trace)

Any ideas on how I can get past this point?

Start by reproducing the upgrade from 10.7.4 to 10.8.0 and run the db:migrate task with --trace. Read lib/gitlab/shell.rb around gitlab_shell_path and version, then config/initializers/5_backend.rb to trace the reported NoMethodError. Done means the migration completes successfully without the Gitlab:Module config error.