Update services.yml
Update services.yml

Not quoting the scalar "%push_notifications.onesignal.endpoint.notifications.class%" starting with the "%" indicator character is deprecated since Symfony 3.1 and will throw a ParseException in 4.0 in "/home/vagrant/Code/training-portal/vendor/bluetea/push-notifications-bundle/Bluetea/PushNotificationsBundle/DependencyInjection/../Resources/config/services.yml"
BlueTeaNL/PushNotificationsBundle