Handle "Canceled" events

[masus04]

Current Behaviour
The following stack trace is raised when trying to enroll for a canceled event:

asvz-bot  | 2023-12-06 13:08:10 INFO     Checking login credentials
asvz-bot  | 2023-12-06 13:08:12 INFO     Login to 'ETH Zürich'
asvz-bot  | 2023-12-06 13:08:14 INFO     Submitted login credentials
asvz-bot  | 2023-12-06 13:08:17 INFO     Valid login credentials
asvz-bot  | 2023-12-06 13:08:21 INFO     Starting enrollment
asvz-bot  | 2023-12-06 13:08:21 INFO     Enrollment is already open. Checking for available places.
asvz-bot  | 2023-12-06 13:08:25 INFO     Lesson has free places
asvz-bot  | 2023-12-06 13:08:25 INFO     Login to 'ETH Zürich'
asvz-bot  | 2023-12-06 13:08:26 INFO     Submitted login credentials
asvz-bot  | 2023-12-06 13:08:29 INFO     Valid login credentials
asvz-bot  | 2023-12-06 13:08:29 INFO     Waiting for enrollment

After which it simply hangs.

Expected Behaviour
The bot should recognize the event has been canceled, print a suitable error message and terminate.