Fix isort issues

src/pretix/base/exporters/items.py

@@ -26,11 +26,11 @@ from django.utils.translation import gettext_lazy as _
 from openpyxl.styles import Alignment
 from openpyxl.utils import get_column_letter
 
+from ...helpers.safe_openpyxl import SafeCell
 from ..channels import get_all_sales_channels
 from ..exporter import ListExporter
 from ..models import ItemMetaValue
 from ..signals import register_data_exporters
-from ...helpers.safe_openpyxl import SafeCell
 
 
 def _max(a1, a2):

src/pretix/presale/views/widget.py

@@ -54,7 +54,9 @@ from lxml import html
 
 from pretix.base.context import get_powered_by
 from pretix.base.i18n import language
-from pretix.base.models import CartPosition, Event, Quota, SubEvent, Voucher, ItemVariation
+from pretix.base.models import (
+    CartPosition, Event, ItemVariation, Quota, SubEvent, Voucher,
+)
 from pretix.base.services.cart import error_messages
 from pretix.base.settings import GlobalSettingsObject
 from pretix.base.templatetags.rich_text import rich_text