Added exception catching to send default email if template file raises any exception

[ecodina]

This PR closes #24919

A try - except block has been added to prevent email failure when a custom template file is used for task error notifications.

Although once Airflow has been correctly configured we should never need the except block, sometimes we may encounter issues when updating the template file. I believe Airflow should always send the email and, in case the template file has any problems, it should just send the default template.

[boring-cyborg]

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[ecodina]

A test failed, but I'd like to argue my case:

In this try - except we will mostly catch the FileNotFoundError, which is explicit.

In any other case (e.g. an IO error), I believe we should still send the email with the default template to make sure we are always notified.

[potiuk]

Yeah. I'd agree. Please add tests covering it and fix those that failed.

[uranusjr]

-1 to this blank catch. It’s probably worthwhile to catch all OSError, but this is way to broad.

[uranusjr]

Better to use {path!r}

[ecodina]

Follwing @uranusjr advice, I replaced the broad exception to only catch OSError (which is the only one that should happen, actually). I have also added a UnitTest:

tests/models/test_taskinstance.py::TestTaskInstance::test_email_alert_with_filenotfound_config PASSED

With this changes, the PR should be ready to be merged.

[potiuk]

Only static checks already fixed in main are failing. MErging.

[boring-cyborg]

Awesome work, congrats on your first merged pull request!