Fixed BNF concept evaluations

tests/test_sheerka_call_evaluators.py

@@ -1,5 +1,5 @@
 # Make sure that the evaluators works as expected
-from core.builtin_concepts import BuiltinConcepts, SuccessConcept
+from core.builtin_concepts import BuiltinConcepts
 from core.concept import Concept
 from core.sheerka import Sheerka, ExecutionContext
 from evaluators.BaseEvaluator import OneReturnValueEvaluator, BaseEvaluator, AllReturnValuesEvaluator
@@ -157,7 +157,7 @@ class EvaluatorAllReduceFooBar(EvaluatorAllWithPriority):
 
     def eval(self, context, return_values):
         super().eval(context, return_values)
-        ret = get_ret_val(context.sheerka, SuccessConcept())
+        ret = get_ret_val(context.sheerka, context.sheerka.new(BuiltinConcepts.SUCCESS))
         ret.parents = return_values
         return ret