Implemented a first and basic version of a Rete rule engine

tests/non_reg/test_sheerka_non_reg_rules.py

@@ -0,0 +1,25 @@
+from core.builtin_concepts_ids import BuiltinConcepts
+from evaluators.PythonEvaluator import PythonEvalError
+from tests.TestUsingMemoryBasedSheerka import TestUsingMemoryBasedSheerka
+
+
+class TestSheerkaNonRegDisplay(TestUsingMemoryBasedSheerka):
+
+    def test_i_can_apply_simple_rule(self):
+        init = [
+            "def concept one as 1",
+            "when __ret.status then test_error()",
+        ]
+
+        sheerka = self.init_scenario(init)
+        sheerka.enable_process_rules = True
+        res = sheerka.evaluate_user_input("one")
+
+        assert len(res) == 1
+        ret = res[0]
+
+        assert not ret.status
+        assert sheerka.isinstance(ret.body, BuiltinConcepts.ERROR)
+        assert isinstance(ret.body.body, PythonEvalError)
+        assert isinstance(ret.body.body.error, Exception)
+        assert ret.body.body.error.args == ("I can raise an error",)