Fixed an encoding error

src/pretix/base/services/cart.py

@@ -3,7 +3,7 @@ from datetime import datetime, timedelta
 from django.conf import settings
 from django.db.models import Q
 from django.utils.timezone import now
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import ugettext as _
 from typing import List, Optional, Tuple
 
 from pretix.base.i18n import LazyLocaleException

src/pretix/base/services/orders.py

@@ -2,9 +2,8 @@ from datetime import datetime, timedelta
 
 from django.conf import settings
 from django.db import transaction
-from django.utils import translation
 from django.utils.timezone import now
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import ugettext as _
 from typing import List
 
 from pretix.base.i18n import (
@@ -79,6 +78,7 @@ def mark_order_paid(order: Order, provider: str=None, info: str=None, date: date
     }, user=user)
     order_paid.send(order.event, order=order)
 
+    with language(order.locale):
         mail(
             order.email, _('Payment received for your order: %(code)s') % {'code': order.code},
             order.event.settings.mail_text_order_paid,