Add missing statsd metric for failing SLA Callback notification

[Jorricks]

There is a statsd metric for failing email notifications but not for failing callbacks.
This PR makes it easier to monitor for failing callbacks to spot them sooner.

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[github-actions]

The PR most likely needs to run full matrix of tests because it modifies parts of the core of Airflow. However, committers might decide to merge it quickly and take the risk. If they don't merge it quickly - please rebase it to the latest main at your convenience, or amend the last commit of the PR, and push it with --force-with-lease.

[Jorricks]

@uranusjr is there a new policy to not merge MRs right away? I am wondering what we are waiting for :)?

[potiuk]

@uranusjr is there a new policy to not merge MRs right away? I am wondering what we are waiting for :)?

I think it was simply overlooked. If you look at the "traffic" in our PRs, you might understand that sometimes some things might simply slip under the radar. Generally speaking it's the author's responsibiliyt to Gently Ping if they see such a situation might happen. You, as author are ultimately mostly interested about this and I bet you have probably orders of magnitude less of PRs that you authored rather than any of the maintainers to approve/merge.

Little empathy goes a long way :). Just gently ping next time.

[Jorricks]

@uranusjr is there a new policy to not merge MRs right away? I am wondering what we are waiting for :)?

I think it was simply overlooked. If you look at the "traffic" in our PRs, you might understand that sometimes some things might simply slip under the radar. Generally speaking it's the author's responsibiliyt to Gently Ping if they see such a situation might happen. You, as author are ultimately mostly interested about this and I bet you have probably orders of magnitude less of PRs that you authored rather than any of the maintainers to approve/merge.

Little empathy goes a long way :). Just gently ping next time.

I understand. I didn't mean anything by my comment, I was just really wondering if I can find the policy on merging PRs somewhere. I appreciate all the work you are doing 🙏
Sorry if it came over harsh

[potiuk]

Sorry if it came over harsh

:) No worries. It just came a bit harsh by the fact that you kinda abandoned it for 20 days (and obviously we did too :) )