Fail nicely if user does not provide artifact files within Nulecule.

atomicapp/nulecule/base.py

@@ -372,6 +372,9 @@ def render(self, provider_key=None, dryrun=False):
         if self._app:
             self._app.render(provider_key=provider_key, dryrun=dryrun)
             return
+        if self.artifacts is None:
+            raise NuleculeException(
+                "No artifacts specified in the Nulecule file")
         context = self.get_context()
         if provider_key and provider_key not in self.artifacts:
             raise NuleculeException(

tests/units/nulecule/test_nulecule_component.py

@@ -238,7 +238,7 @@ def test_render_for_external_app(self):
         provider_key = 'some-provider'
         dryrun = False
 
-        nc = NuleculeComponent(name='some-app', basepath='some/path')
+        nc = NuleculeComponent(name='some-app', basepath='some/path', artifacts="/foo/bar")
         nc._app = mock_nulecule
         nc.render(provider_key, dryrun)
 
@@ -259,6 +259,17 @@ def test_render_for_local_app_with_missing_artifacts_for_provider(self):
 
         self.assertRaises(NuleculeException, nc.render, provider_key, dryrun)
 
+    def test_render_for_local_app_with_missing_artifacts_from_nulecule(self):
+        """
+        Test rendering a Nulecule component with no artifacts provided in the
+        Nulecule file.
+        """
+        nc = NuleculeComponent(name='some-app', basepath='some/path')
+        nc.config = {}
+
+        with self.assertRaises(NuleculeException):
+            nc.render()
+
     @mock.patch('atomicapp.nulecule.base.NuleculeComponent.get_context')
     @mock.patch('atomicapp.nulecule.base.NuleculeComponent.'
                 'get_artifact_paths_for_provider')