Apply suggestions from code review

Co-authored-by: luelista <mira@teamwiki.de>

src/pretix/presale/views/cart.py

@@ -844,7 +844,7 @@ class AnswerDownload(EventViewMixin, View):
         filename = '{}-cart-{}'.format(
             self.request.event.slug.upper(),
             os.path.basename(answer.file.name).split('.', 1)[1]
-        ).encode("ascii", "ignore")
+        )
         resp = FileResponse(
             answer.file,
             filename=filename,

src/pretix/presale/views/order.py

@@ -1236,7 +1236,8 @@ class OrderDownloadMixin:
             else:
                 return FileResponse(
                     value.file.file,
-                    filename="-".join(self.request.event.slug.upper(), self.order.code, self.output.identifier) + value.extension,
+                    filename="{}-{}-{}{}".format(
+                        self.request.event.slug.upper(), self.order.code, self.output.identifier, value.extension),
                     content_type=value.type
                 )
         else: