In the test_it_sends_link testcase, explicitly set the USE_PAYMENTS setting. This way tests work regardless of what's in the environment variable or local_settings.py file.

hc/accounts/tests/test_signup.py

@@ -8,6 +8,7 @@ from django.conf import settings
 
 
 class SignupTestCase(TestCase):
+    @override_settings(USE_PAYMENTS=False)
     def test_it_sends_link(self):
         form = {"identity": "alice@example.org"}