Migrations might cause issues here... there's already a `0002_auto__add_textbannervariation__del_field_textbanner_text.py` in the repo now and running migrations after checking this PR out returns:
 `! Migration banners:0002_auto__add_textbannervariation__del_field_textbanner_text should not have been applied before banners:0002_auto__add_firefoxupgradebannervariation__add_firefoxupgradebanner but was.`