Error 500 with "undefined method `main_language'"
Accessing any GitLab page after updating to 8.6.0 or 8.6.1 CE (Omnibus) and correctly running gitlab-ctl reconfigure leads to:
Started GET "/" for 127.0.0.1 at 2016-03-23 16:23:39 +0100
Processing by RootController#index as HTML
Read fragment views/groups/2-20150623093513433515000/projects/1-20160322142439938487000/root/index/application_settings/1-20160125114729133877000/v2.2/success/86aa46c6c228c49e9392077e9782690a (0.2ms)
Completed 500 Internal Server Error in 256ms (ActiveRecord: 19.5ms)
ActionView::Template::Error (undefined method `main_language' for #<Project:0x00000007036b30>):
28: = project.name
29:
30: .controls
31: - if project.main_language
32: %span
33: = project.main_language
34: - if ci_commit
app/views/shared/projects/_project.html.haml:31:in `block in _app_views_shared_projects__project_html_haml___1614823772075910883_58988740'
app/views/shared/projects/_project.html.haml:14:in `_app_views_shared_projects__project_html_haml___1614823772075910883_58988740'
app/views/shared/projects/_list.html.haml:16:in `block in _app_views_shared_projects__list_html_haml___4403536587211884541_58574200'
app/views/shared/projects/_list.html.haml:14:in `_app_views_shared_projects__list_html_haml___4403536587211884541_58574200'
app/views/dashboard/projects/_projects.html.haml:1:in `_app_views_dashboard_projects__projects_html_haml___3522197525017315537_58508840'
app/views/dashboard/projects/index.html.haml:14:in `_app_views_dashboard_projects_index_html_haml__4521317621515333910_57434060'
app/controllers/dashboard/projects_controller.rb:15:in `index'
app/controllers/root_controller.rb:13:in `index'
lib/gitlab/middleware/go.rb:16:in `call'
This seems to be the same as in #14504 (closed), which was closed despite not being fixed. I had high hopes for a fix in 8.6.1, but it seems the problem was not yet taken care of by the maintainers.
Related/duplicate of #14504 (closed) and #14347 (closed)