When checking for the compatibility of the expert brain with the policy brain, we will remove the action descriptions from the dictionary of things we need to compare. This is to prevent the case where a user has different descriptions for his actions but still wants to train a brain using expert demonstrations. (#2517)

ml-agents/mlagents/trainers/bc/offline_trainer.py

         expert_brain = copy.deepcopy(brain_params.__dict__)
         policy_brain.pop("brain_name")
         expert_brain.pop("brain_name")
+        policy_brain.pop("vector_action_descriptions")
+        expert_brain.pop("vector_action_descriptions")
         if expert_brain != policy_brain:
             raise UnityTrainerException(
                 "The provided demonstration is not compatible with the "