jsonresponse: make sure exception message is a serializable string (#11162)

passerelle/utils/jsonresponse.py

@@ -11,6 +11,7 @@ from django.http import HttpResponse, Http404
 from django.conf import settings
 from django.core.exceptions import ObjectDoesNotExist, PermissionDenied
 from django.core.serializers.json import DjangoJSONEncoder
+from django.utils.translation import force_text
 
 DEFAULT_DEBUG = getattr(settings, 'JSONRESPONSE_DEFAULT_DEBUG', False)
 CALLBACK_NAME = getattr(settings, 'JSONRESPONSE_CALLBACK_NAME', 'callback')
@@ -304,7 +305,7 @@ class to_json(object):
 
         err_class = err_module + err.__class__.__name__
 
-        err_desc = str(err)
+        err_desc = force_text(err)
 
         return {
             "err": 1,