Make TaskHandler properly handle missing attribute on server reload. Resolve #3620

CHANGELOG.md

@@ -36,6 +36,8 @@ did not add it to the handler's object (Griatch)
   respected (Griatch)
 - [Fix][issue3624]: Setting tags with integer names caused errors on postgres (Griatch)
 - [Fix][issue3615]: Using `print()` in `py` caused an infinite loop (Griatch)
+- [Fix][issue3620]: Better handle TaskHandler running against an attribute that
+  was removed since last reload (Griatch)
 - [Docs][issue3591]: Fix of NPC reaction tutorial code (Griatch)
 - Docs: Tutorial fixes (Griatch, aMiss-aWry, feyrkh)
 
@@ -46,6 +48,7 @@ did not add it to the handler's object (Griatch)
 [issue3612]: https://github.com/evennia/evennia/issues/3612
 [issue3624]: https://github.com/evennia/evennia/issues/3624
 [issue3615]: https://github.com/evennia/evennia/issues/3615
+[issue3620]: https://github.com/evennia/evennia/issues/3620
 [pull3595]: https://github.com/evennia/evennia/pull/3595
 [pull3533]: https://github.com/evennia/evennia/pull/3533
 [pull3594]: https://github.com/evennia/evennia/pull/3594

evennia/scripts/taskhandler.py

@@ -5,13 +5,12 @@ Module containing the task handler for Evennia deferred tasks, persistent or not
 from datetime import datetime, timedelta
 from pickle import PickleError
 
-from twisted.internet import reactor
-from twisted.internet.defer import CancelledError as DefCancelledError
-from twisted.internet.task import deferLater
-
 from evennia.server.models import ServerConfig
 from evennia.utils.dbserialize import dbserialize, dbunserialize
 from evennia.utils.logger import log_err
+from twisted.internet import reactor
+from twisted.internet.defer import CancelledError as DefCancelledError
+from twisted.internet.task import deferLater
 
 TASK_HANDLER = None
 
@@ -251,7 +250,12 @@ class TaskHandler:
                     to_save = True
                     continue
 
+                try:
                     callback = getattr(obj, method)
+                except Exception as e:
+                    log_err(f"TaskHandler: Unable to load task {task_id} (disabling it): {e}")
+                    to_save = True
+                    continue
             self.tasks[task_id] = (date, callback, args, kwargs, True, None)
 
         if self.stale_timeout > 0:  # cleanup stale tasks.