def clean_cover(self):
cover = self.cleaned_data['cover']
if cover.name.rsplit('.', 1)[-1].lower() not in ('jpg', 'jpeg', 'png', 'gif', 'tif', 'tiff'):
def clean_cover(self):
cover = self.cleaned_data['cover']
if cover.name.rsplit('.', 1)[-1].lower() not in ('jpg', 'jpeg', 'png', 'gif', 'tif', 'tiff'):