Auto-scheduled emails

Co-authored-by: Raphael Michel <michel@rami.io>

src/pretix/base/models/event.py

@@ -75,7 +75,6 @@ from .organizer import Organizer, Team
 
 
 class EventMixin:
-
     def clean(self):
         if self.presale_start and self.presale_end and self.presale_start > self.presale_end:
             raise ValidationError({'presale_end': _('The end of the presale period has to be later than its start.')})
@@ -494,11 +493,17 @@ class Event(EventMixin, LoggedModel):
     )
     seating_plan = models.ForeignKey('SeatingPlan', on_delete=models.PROTECT, null=True, blank=True,
                                      related_name='events')
+
+    last_modified = models.DateTimeField(
+        auto_now=True, db_index=True
+    )
+
     sales_channels = MultiStringField(
         verbose_name=_('Restrict to specific sales channels'),
         help_text=_('Only sell tickets for this event on the following sales channels.'),
         default=default_sales_channels,
     )
+
     objects = ScopedManager(organizer='organizer')
 
     class Meta:
@@ -1255,13 +1260,14 @@ class SubEvent(EventMixin, LoggedModel):
     )
     seating_plan = models.ForeignKey('SeatingPlan', on_delete=models.PROTECT, null=True, blank=True,
                                      related_name='subevents')
-    last_modified = models.DateTimeField(
-        auto_now=True, db_index=True
-    )
 
     items = models.ManyToManyField('Item', through='SubEventItem')
     variations = models.ManyToManyField('ItemVariation', through='SubEventItemVariation')
 
+    last_modified = models.DateTimeField(
+        auto_now=True, db_index=True
+    )
+
     objects = ScopedManager(organizer='event__organizer')
 
     class Meta:

src/pretix/base/models/orders.py

@@ -899,7 +899,7 @@ class Order(LockModel, LoggedModel):
             return str(e)
         return True
 
-    def send_mail(self, subject: str, template: Union[str, LazyI18nString],
+    def send_mail(self, subject: Union[str, LazyI18nString], template: Union[str, LazyI18nString],
                   context: Dict[str, Any]=None, log_entry_type: str='pretix.event.order.email.sent',
                   user: User=None, headers: dict=None, sender: str=None, invoices: list=None,
                   auth=None, attach_tickets=False, position: 'OrderPosition'=None, auto_email=True,
@@ -942,7 +942,7 @@ class Order(LockModel, LoggedModel):
 
             try:
                 email_content = render_mail(template, context)
-                subject = subject.format_map(TolerantDict(context))
+                subject = str(subject).format_map(TolerantDict(context))
                 mail(
                     recipient, subject, template, context,
                     self.event, self.locale, self, headers=headers, sender=sender,