Fix e2e tests (#520)

added a migration to kill waffle tables causing unmanaged postgres
dependencies

src/core/migrations/0005_fix_waffle_truncate_issue.py

@@ -0,0 +1,18 @@
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+    """
+    Migration for issue: cannot truncate a table referenced in a foreign key constraint: Table "waffle_flag_groups" references "auth_group".
+    See more: https://github.com/django-waffle/django-waffle/issues/317#issuecomment-488398832
+    """
+
+    dependencies = [
+        ("core", "0004_featureflag"),
+        ("waffle", "__latest__"),
+    ]
+
+    operations = [
+        migrations.RunSQL("DROP TABLE IF EXISTS waffle_flag_groups"),
+        migrations.RunSQL("DROP TABLE IF EXISTS waffle_flag_users"),
+    ]