Failing get all challenges endpoints

[gchhablani]

{{host_name}}/api/challenges/challenge/all/all/all
{{host_name}}/api/challenges/challenge/all/all/public
{{host_name}}/api/challenges/challenge/all/unapproved/all
{{host_name}}/api/challenges/challenge/all/unapproved/public

These four API calls are failing with 500. I am not exactly sure why. Adding try-except does not help. Needs further investigation.

[b9aurav]

@gchhablani Can you assign it to me? I would be happy to work on it.