Raise error when trying to create second cluster

app/services/clusters/create_service.rb

@@ -5,7 +5,7 @@ module Clusters
     def execute(access_token)
       @access_token = access_token
 
-      return unless can_create_cluster?
+      raise Exception.new('Instance does not support multiple clusters') unless can_create_cluster?
 
       create_cluster.tap do |cluster|
         ClusterProvisionWorker.perform_async(cluster.id) if cluster.persisted?

spec/services/clusters/create_service_spec.rb

@@ -83,7 +83,7 @@ describe Clusters::CreateService do
 
       it 'does not create a cluster' do
         expect(ClusterProvisionWorker).not_to receive(:perform_async)
-        expect { result }.to change { Clusters::Cluster.count }.by(0)
+        expect { result }.to raise_error(Exception).and change { Clusters::Cluster.count }.by(0)
       end
     end
   end