test: skip some tests if mako not installed

also change corresponding tox env to 'nox' to reflect its "bare-bones"
nature and not just a lack of 'db'

tests/test_app.py

@@ -398,6 +398,11 @@ class TestAppHandler(FileConfigTestCase):
         self.assertIsInstance(auth, AuthHandler)
 
     def test_get_email_handler(self):
+        try:
+            import mako
+        except ImportError:
+            pytest.skip("test not relevant without mako")
+
         from wuttjamaican.email import EmailHandler
 
         mail = self.app.get_email_handler()
@@ -409,7 +414,12 @@ class TestAppHandler(FileConfigTestCase):
         people = self.app.get_people_handler()
         self.assertIsInstance(people, PeopleHandler)
 
-    def test_get_send_email(self):
+    def test_send_email(self):
+        try:
+            import mako
+        except ImportError:
+            pytest.skip("test not relevant without mako")
+
         from wuttjamaican.email import EmailHandler
 
         with patch.object(EmailHandler, 'send_email') as send_email: