Support Wagtail 4.2 (#1)

Co-authored-by: nick.moreton <nick.moreton@torchbox.com>
Co-authored-by: Nick Moreton <nick.moreton@torchbox.com>
Reviewed-on: #1

tests/conftest.py

@@ -1,8 +1,6 @@
 import pytest
 
-pytest_plugins = [
-    'tests.fixtures'
-]
+pytest_plugins = ["tests.fixtures"]
 
 
 @pytest.fixture(autouse=True)
@@ -10,9 +8,9 @@ def enable_db_access(db):
     pass
 
 
-@pytest.fixture(scope='session')
+@pytest.fixture(scope="session")
 def django_db_setup(django_db_setup, django_db_blocker):
-    from wagtail.core.models import Page, Site
+    from wagtail.models import Page, Site
 
     with django_db_blocker.unblock():
         # Remove some initial data that is brought by the tests.site module