Added custom error pages

src/pretix/base/views/cachedfiles.py

@@ -0,0 +1,22 @@
+from django.http import HttpResponse
+from django.shortcuts import get_object_or_404, redirect
+from django.utils.functional import cached_property
+from django.views.generic import TemplateView
+
+from pretix.base.models import CachedFile
+
+
+class DownloadView(TemplateView):
+    template_name = "pretixbase/cachedfiles/pending.html"
+
+    @cached_property
+    def object(self):
+        return get_object_or_404(CachedFile, id=self.kwargs['id'])
+
+    def get(self, request, *args, **kwargs):
+        if 'ajax' in request.GET:
+            return HttpResponse('1' if self.object.file else '0')
+        elif self.object.file:
+            return redirect(self.object.file.url)
+        else:
+            return super().get(request, *args, **kwargs)