use chisme update_layer

[agathanatasha]

Update training-operator to use the update_layer function in chisme, updated tests to match
CI would fail until this pr is merged and published. Tested locally with git+https://github.com/canonical/charmed-kubeflow-chisme@KF-605/update-layer-handler in requirements.txt

Related to #94

[DnPlas]

Let's be careful with .*ignore files, they might make the diff confusing. You'd want to add these files if you are changing something in the CI or in the structure of the repo. You can keep it here for now, let's avoid this in future PRs.

[agathanatasha]

noted. I think this file is created from running unit test. I wanted to avoid committing it. It is not currently committed.

[DnPlas]

Thanks @agathanatasha, your implementation is fine, I don't have much to say about it, though I am thinking if these try/catch blocks that we are repeating can live in another helper method (I know we are trying to move away from that), as it seems redundant. What are your thoughts on that?

[agathanatasha]

Thanks @agathanatasha, your implementation is fine, I don't have much to say about it, though I am thinking if these try/catch blocks that we are repeating can live in another helper method (I know we are trying to move away from that), as it seems redundant. What are your thoughts on that?

Not for now. I can't tell whether it would be reused more or less at this point in time. We can create a helper method in the future if it would be reused more.