lib: add helper method for 400 response with message

passbook/lib/views.py

@@ -1,5 +1,6 @@
 """passbook helper views"""
-
+from django.http import HttpRequest, HttpResponse
+from django.shortcuts import render
 from django.views.generic import CreateView
 from guardian.shortcuts import assign_perm
 
@@ -22,3 +23,8 @@ class CreateAssignPermView(CreateView):
             )
             assign_perm(full_permission, self.request.user, self.object)
         return response
+
+
+def bad_request_message(request: HttpRequest, message: str) -> HttpResponse:
+    """Return generic error page with message, with status code set to 400"""
+    return render(request, "error/400.html", {"message": message}, status=400)