[Job] Wrong Exception Handling For Dashboard

[KeplerC]

The exception thrown by the dashboard.py is misleading

it throws Cluster does not exist in all cases.

To reproduce

ssh sky-jobs-controller-hash 
curl localhost:5000  # normal response
cd ~/.sky && mv sky_ray.yml sky_ray.yml_ # introduce a simple bug 
curl localhost:5000 
cat ~/.sky/job-dashboard.log 

Error log:

~/.sky$ cat ~/.sky/job-dashboard.log 
 * Serving Flask app 'dashboard'
 * Debug mode: off
INFO:werkzeug:WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
 * Running on http://127.0.0.1:5000
INFO:werkzeug:Press CTRL+C to quit
INFO:werkzeug:127.0.0.1 - - [07/Jan/2025 02:02:09] "GET / HTTP/1.1" 200 -
ERROR:dashboard:Exception on / [GET]
sky.exceptions.ClusterDoesNotExist: Cluster 'sky-jobs-controller-726f1974' does not exist.

it throws cluster does not exists in any circumstances.

• sky -v: PLEASE_FILL_IN
• sky -c: PLEASE_FILL_IN

[Mizokuiam]

Thank you for raising this issue! I'll look into it and try to help if I can.