Address nose tests deprecation issues

The Python 3.8 CI testing is failing with an error because we haven't
addressed the nose tests support deprecation by renaming the setup()
method to setup_method().

test/unit/defaults_test.py

@@ -8,7 +8,7 @@
 
 
 class TestDefaults(object):
-    def setup(self):
+    def setup_method(self):
         self.defaults = Defaults()
 
     def test_get_migration_config_file(self):