Guaranteed to run cleanup functions in error conditions

ctabus/internal/notification.py

@@ -1,4 +1,5 @@
 from concurrent.futures import ThreadPoolExecutor
+import atexit
 import os
 import shlex
 import shutil
@@ -30,6 +31,7 @@ class NotificationManager:
         self._posting = False
         self._poster = None
         self._live = True
+        atexit.register(self._cleanup)
 
     def on_done(self):
         pass