500 error on new cluster integration

---

Summary

I'm trying to connect to newly created external kubernetes cluster from CI/CD -> Clusters page

Steps to reproduce

Create new cluster at project's CI/CD -> Clusters page

What is the current bug behavior?

500 error

What is the expected correct behavior?

Cluster is connected

Relevant logs and/or screenshots

Started POST "/images/autodevops/clusters/providers/user" for *.*.*.* at 2018-01-22 07:17:59 +0000

Processing by Projects::Clusters::UserController#create as HTML

Parameters: {"utf8"=>"✓", "authenticity_token"=>"[FILTERED]", "cluster"=>{"name"=>"Test", "environment_scope"=>"*", "platform_kubernetes_attributes"=>{"api_url"=>"<URL>", "ca_cert"=>"-----BEGIN CERTIFICATE-----******-----END CERTIFICATE-----", "token"=>"[FILTERED]", "namespace"=>""}}, "namespace_id"=>"images", "project_id"=>"autodevops"}

Completed 500 Internal Server Error in 77ms (ActiveRecord: 5.5ms)

Started POST "/api/v4/jobs/request" for *.*.*.* at 2018-01-22 07:18:00 +0000

Sending event 8c77a9a2004647479f3735ecaddd1efe to Sentry

ArgumentError (key must be 32 bytes or longer):

app/services/clusters/create_service.rb:18:in `create_cluster'
app/services/clusters/create_service.rb:10:in `execute'
app/controllers/projects/clusters/user_controller.rb:14:in `create'
lib/gitlab/i18n.rb:47:in `with_locale'
lib/gitlab/i18n.rb:53:in `with_user_locale'
app/controllers/application_controller.rb:324:in `set_locale'
lib/gitlab/middleware/multipart.rb:93:in `call'
lib/gitlab/request_profiler/middleware.rb:14:in `call'
lib/gitlab/middleware/go.rb:18:in `call'
lib/gitlab/etag_caching/middleware.rb:11:in `call'
lib/gitlab/middleware/rails_queue_duration.rb:22:in `call'
lib/gitlab/metrics/rack_middleware.rb:15:in `block in call'
lib/gitlab/metrics/transaction.rb:52:in `run'
lib/gitlab/metrics/rack_middleware.rb:15:in `call'
lib/gitlab/middleware/read_only.rb:31:in `call'
lib/gitlab/request_context.rb:18:in `call'
lib/gitlab/metrics/requests_rack_middleware.rb:27:in `call'

Results of GitLab environment info

Expand for output related to GitLab environment info

System information
System:         Ubuntu 14.04
Current User:   git
Using RVM:      no
Ruby Version:   2.3.5p376
Gem Version:    2.5.2.1
Bundler Version:1.16.1
Rake Version:   12.3.0
Redis Version:  2.8.4
Git Version:    2.15.1
Sidekiq Version:5.0.4
Go Version:     unknown
GitLab information
Version:        10.3.5
Revision:       7c30d48
Directory:      /home/git/gitlab
DB Adapter:     postgresql
URL:            
HTTP Clone URL: 
SSH Clone URL:  git@:some-group/some-project.git
Using LDAP:     no
Using Omniauth: yes
Omniauth Providers: github, bitbucket
GitLab Shell
Version:        5.10.2
Repository storage paths:

• default: /home/git/data/repositories Hooks: /home/git/gitlab-shell/hooks Git: /usr/bin/git