Fix tests and rename request variable in specs to perform_request

Explanation: Using the variable name `request` might interfere with methods in Rails core system prevent successful test execution. See this issue: https://github.com/turbolinks/turbolinks-rails/issues/38

spec/policies/code_ocean/error_policy_spec.rb

@@ -1,6 +1,6 @@
 require 'rails_helper'
 
-describe ErrorPolicy do
+describe CodeOcean::ErrorPolicy do
   subject { described_class }
 
   let(:error) { FactoryBot.build(:error) }