Refactor code quality issues (#2001)

src/pretix/plugins/checkinlists/exporters.py

@@ -159,7 +159,7 @@ class CheckInListMixin(BaseExporter):
             ), self.event.timezone)
             qs = qs.filter(subevent__date_from__lt=dt)
 
-        o = tuple()
+        o = ()
         if self.event.has_subevents and not cl.subevent:
             o = ('subevent__date_from', 'subevent__name')
 

src/pretix/plugins/reports/exporters.py

@@ -616,7 +616,7 @@ class OrderTaxListReport(MultiSheetListExporter):
         elif sheet == 'companies':
             yield from self.iterate_companies(form_data)
 
-    def _combine(self, *qs, keys=tuple()):
+    def _combine(self, *qs, keys=()):
         cache = {}
 
         def kf(r):