Fix db/fixtures

db/fixtures/development/99_common_metrics.rb

 # frozen_string_literal: true
 
-require_relative '../importers/common_metrics_importer.rb'
+require Rails.root.join('db/importers/common_metrics_importer.rb')
 
 ::Importers::CommonMetricsImporter.new.execute

db/fixtures/production/999_common_metrics.rb

 # frozen_string_literal: true
 
-require_relative '../importers/common_metrics_importer.rb'
+require Rails.root.join('db/importers/common_metrics_importer.rb')
 
 ::Importers::CommonMetricsImporter.new.execute

db/migrate/20180831164909_import_common_metrics.rb

@@ -3,7 +3,7 @@
 class ImportCommonMetrics < ActiveRecord::Migration
   include Gitlab::Database::MigrationHelpers
 
-  require_relative '../importers/common_metrics_importer.rb'
+  require Rails.root.join('db/importers/common_metrics_importer.rb')
 
   DOWNTIME = false
 

doc/development/prometheus_metrics.md

@@ -31,7 +31,9 @@ After you add or change existing _common_ metric you have to create a new databa
 
 ```ruby
 class ImportCommonMetrics < ActiveRecord::Migration
-  require_relative '../importers/common_metrics_importer.rb'
+  include Gitlab::Database::MigrationHelpers
+
+  require Rails.root.join('db/importers/common_metrics_importer.rb')
 
   DOWNTIME = false