Fix error description on exception

[noissue]

pulp_smash/pulp3/bindings.py

@@ -36,7 +36,7 @@ class PulpTaskError(Exception):
 
     def __init__(self, task):
         """Provide task info to exception."""
-        description = task.error["description"]
+        description = task.to_dict()["error"]["description"]
         super().__init__(self, f"Pulp task failed ({description})")
         self.task = task