Apply suggestions from code review

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

src/pretix/base/datasync/datasync.py

@@ -245,6 +245,9 @@ class OutboundSyncProvider:
                     sq.in_flight_since = now()
                     sq.save()
                 except DatabaseError:
+                    # Either select_for_update failed to lock the row, or we couldn't set in_flight
+                    # as this order is already in flight (UNIQUE violation). In either case, we ignore
+                    # this order for now.
                     continue
                 try:
                     mapped_objects = self.sync_order(sq.order)

src/pretix/base/models/datasync.py

@@ -51,7 +51,7 @@ class OrderSyncQueue(models.Model):
     not_before = models.DateTimeField(blank=False, null=False, db_index=True)
     need_manual_retry = models.CharField(blank=True, null=True, max_length=20, choices=[
         ('exceeded', _('Temporary error, auto-retry limit exceeded')),
-        ('permanent', _('Misconfiguration, please check provider settings')),
+        ('permanent', _('Provider reported a permanent error')),
         ('config', _('Misconfiguration, please check provider settings')),
         ('internal', _('System error, needs manual intervention')),
         ('timeout', _('System error, needs manual intervention')),