Let's return an error when attachment not found

bt/views.py

@@ -284,9 +284,12 @@ class ViolationSearchView(SearchView):
 def get_attach(request,id):
     f = get_object_or_404(Attachment, pk=id)
     wrapper = FileWrapper(f.storage)
-    response=HttpResponse(wrapper, content_type=f.type)
-    response['Content-Disposition'] = 'attachment; filename="%s"' % f.name
-    response['Content-Length'] = f.storage.size
+    try:
+        response=HttpResponse(wrapper, content_type=f.type)
+        response['Content-Disposition'] = 'attachment; filename="%s"' % f.name
+        response['Content-Length'] = f.storage.size
+    except:
+        response=HttpResponseNotFound('<h1>Document not found.</h1>')
     return response
 
 class ViolationCsvList(ListView):