Creating new project partially fails (Unable to save project), then Services and Webhooks are inaccessible with a 500 error

Summary

In Gitlab CE 8.11.5 creating a new project works as far as creating a Git repository that can be cloned and pushed to, but production.log contains this error message:

Unable to save project. Error: undefined method `confidential_issues_events=' for #<BugzillaService:0x0000000c3d4440>Project ID: 618

Then, when trying to access that new project's settings or webhooks a 500 error is displayed and production.log contains a similar error message:

Started GET "/somegroup/testproject1/services" for 192.168.12.12 at 2016-09-14 04:14:36 +0200
Processing by Projects::ServicesController#index as HTML
  Parameters: {"namespace_id"=>"somegroup", "project_id"=>"testproject1"}
Completed 500 Internal Server Error in 210ms (ActiveRecord: 38.1ms)

NoMethodError (undefined method `confidential_issues_events=' for #<BugzillaService:0x0000000cd9d698>):
  app/models/project.rb:716:in `block in build_missing_services'
  app/models/project.rb:706:in `each'
  app/models/project.rb:706:in `build_missing_services'
  app/controllers/projects/services_controller.rb:13:in `index'
  lib/gitlab/request_profiler/middleware.rb:15:in `call'
  lib/gitlab/middleware/go.rb:16:in `call'


Started GET "/somegroup/testproject1/services" for 192.168.12.12 at 2016-09-14 04:14:36 +0200
Processing by Projects::ServicesController#index as HTML
  Parameters: {"namespace_id"=>"somegroup", "project_id"=>"testproject1"}
Completed 500 Internal Server Error in 209ms (ActiveRecord: 35.4ms)

NoMethodError (undefined method `confidential_issues_events=' for #<BugzillaService:0x00000005a63d08>):
  app/models/project.rb:716:in `block in build_missing_services'
  app/models/project.rb:706:in `each'
  app/models/project.rb:706:in `build_missing_services'
  app/controllers/projects/services_controller.rb:13:in `index'
  lib/gitlab/request_profiler/middleware.rb:15:in `call'
  lib/gitlab/middleware/go.rb:16:in `call'

Steps to reproduce

Create a new project and observe production.log, then try accessing that project's services or webhooks.

Expected behavior

Services, webhooks should be accessible, not failing with a 500 error.

Actual behavior

See summary

Relevant logs and/or screenshots

Unable to save project. Error: undefined method `confidential_issues_events=' for #<BugzillaService:0x0000000c3d4440>Project ID: 618

Started GET "/somegroup/testproject1/services" for 192.168.12.12 at 2016-09-14 04:14:36 +0200
Processing by Projects::ServicesController#index as HTML
  Parameters: {"namespace_id"=>"somegroup", "project_id"=>"testproject1"}
Completed 500 Internal Server Error in 210ms (ActiveRecord: 38.1ms)

NoMethodError (undefined method `confidential_issues_events=' for #<BugzillaService:0x0000000cd9d698>):
  app/models/project.rb:716:in `block in build_missing_services'
  app/models/project.rb:706:in `each'
  app/models/project.rb:706:in `build_missing_services'
  app/controllers/projects/services_controller.rb:13:in `index'
  lib/gitlab/request_profiler/middleware.rb:15:in `call'
  lib/gitlab/middleware/go.rb:16:in `call'


Started GET "/somegroup/testproject1/services" for 192.168.12.12 at 2016-09-14 04:14:36 +0200
Processing by Projects::ServicesController#index as HTML
  Parameters: {"namespace_id"=>"somegroup", "project_id"=>"testproject1"}
Completed 500 Internal Server Error in 209ms (ActiveRecord: 35.4ms)

NoMethodError (undefined method `confidential_issues_events=' for #<BugzillaService:0x00000005a63d08>):
  app/models/project.rb:716:in `block in build_missing_services'
  app/models/project.rb:706:in `each'
  app/models/project.rb:706:in `build_missing_services'
  app/controllers/projects/services_controller.rb:13:in `index'
  lib/gitlab/request_profiler/middleware.rb:15:in `call'
  lib/gitlab/middleware/go.rb:16:in `call'

Output of checks

Results of GitLab application Check

Results of GitLab environment info

System information
System:         Ubuntu 14.04
Current User:   git
Using RVM:      no
Ruby Version:   2.3.1p112
Gem Version:    2.6.6
Bundler Version:2.3.0
Rake Version:   10.5.0
Sidekiq Version:4.1.4

GitLab information
Version:        8.11.5
Revision:       f1ce997
Directory:      /opt/gitlab/embedded/service/gitlab-rails
DB Adapter:     postgresql
URL:            https://gitlab.example.com
HTTP Clone URL: https://gitlab.example.com/some-group/some-project.git
SSH Clone URL:  ssh://git@gitlab.example.com:1234/some-group/some-project.git
Using LDAP:     yes
Using Omniauth: no

GitLab Shell
Version:        3.4.0
Repository storage paths:
- default:      /projects/gitlab/git-data/repositories
Hooks:          /opt/gitlab/embedded/service/gitlab-shell/hooks/
Git:            /opt/gitlab/embedded/bin/git