blueprints: fix error when imported blueprint is invalid (#5414)

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

authentik/blueprints/api.py

@@ -49,7 +49,8 @@ class BlueprintInstanceSerializer(ModelSerializer):
         context = self.instance.context if self.instance else {}
         valid, logs = Importer(content, context).validate()
         if not valid:
-            raise ValidationError(_("Failed to validate blueprint"), *[x["msg"] for x in logs])
+            text_logs = "\n".join([x["event"] for x in logs])
+            raise ValidationError(_("Failed to validate blueprint: %(logs)s" % {"logs": text_logs}))
         return content
 
     def validate(self, attrs: dict) -> dict: