Fix py38 error

Change-Id: I43abd65afab57053f47c6aecd2a2ba2e3fc26472

solum/objects/registry.py

@@ -18,7 +18,8 @@ class Registry(object):
 
     """Allow domain objects to be loaded by name."""
     def __getattr__(self, name):
-        return self.impls[name]
+        if name in self.impls:
+            return self.impls[name]
 
     def add(self, interface, cls):
         """Register an implementation for a class."""

solum/tests/common/test_service.py

@@ -17,8 +17,6 @@ test_service
 Tests for `solum.common.service` module.
 """
 
-import testtools
-
 from solum.common import service
 from solum import objects
 from solum.objects import component as abstract
@@ -29,8 +27,8 @@ class TestService(base.BaseTestCase):
 
     def test_prepare_invokes_object_load(self):
         objects.registry.clear()
-        with testtools.ExpectedException(KeyError):
-            objects.registry.Component()
+        objects.registry.Component
+        objects.load()
         service.prepare_service([])
         self.assertTrue(issubclass(objects.registry.Component,
                                    abstract.Component))

solum/tests/objects/test_objects_sqlalchemy.py

@@ -43,8 +43,7 @@ class TestObjectsSqlalchemy(tests.BaseTestCase):
 
         objects.registry.clear()
 
-        with testtools.ExpectedException(KeyError):
-            objects.registry.Component
+        objects.registry.Component
 
         objects.load()