grant that full task is not broken here

[EduardoJM]

• https://github.com/tunelator/tunelator-backend/blob/main/tunelator/core/celery.py#L51

• [x] create test case for check_user_late_mails raising FileNotFoundError
• [x] create test case for periodic_check_mails raising this error into check_user_late_mails
• [x] use contextlib supress to prevent those errors.

[EduardoJM]

Gots an file not found error into an check realy stop the job. Use contextlib supress and write an test for throwing exceptions