Make sure you have the same PicketLink version on WildFly 10 as you have on WildFly 8.
Indeed, WildFly 8.2.0 has picketlink-federation-2.6.0.Final as a module, while WildFly 10 features 2.5.5.SP1.
2.7.0.Final is necessary and sufficient for my needs. So I always had to install this version on top of all WildFly versions. Also I tried latest 2.7.1.Final but encountered an issue with redirect binding and downgraded back to 2.7.0. So PicketLink version upgrade should be made with caution.
Thank you for your help. I upgraded PicketLink version from 2.5 to 2.6 on WildFly 10.