fixed a couple of errors spotted in production

app/services/projects/import_export/export_service.rb

@@ -50,7 +50,7 @@ module Projects
       end
       def notify_error
-        notification_service.project_not_exported(@project, @current_user, @shared.errors.join(', '))
+        notification_service.project_not_exported(@project, @current_user, @shared.errors)
       end
     end
   end

lib/gitlab/import_export.rb

@@ -21,7 +21,7 @@ module Gitlab
     end
     def config_file
-      'lib/gitlab/import_export/import_export.yml'
+      File.join(Rails.root, 'lib/gitlab/import_export/import_export.yml')
     end
     def version_filename