[data_interfaces] JujuVersion.from_environ() is deprecated since Ops 2.19

[dwilding]

Recently I noticed the following warning when using data_interfaces:

data_interfaces.py:998: DeprecationWarning: JujuVersion.from_environ() is deprecated, use self.model.juju_version instead
    self._jujuversion = JujuVersion.from_environ()

In Ops 2.19.0 we added Model.juju_version and marked JujuVersion.from_environ() as deprecated.

Since data_interfaces requires Ops 2.0.0 or above (in PYDEPS), I'm not sure whether it would be possible to drop support for JujuVersion.from_environ() in data_interfaces. But I thought it would be useful to ask a couple of questions:

• Is there a minimum Ops version that needs to be supported by data_interfaces?

• If data_interfaces needs to support Ops versions prior to 2.19.0, would it be worth adding conditional logic to avoid the warning in newer Ops versions?

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The internal ticket has been created: https://warthogs.atlassian.net/browse/DPE-7407.

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[Gu1nness]

We have support for charms that are still on juju 2.9 so I would expect that we still support some older ops versions above 2.0. The doc says that it supports only ops 2>= 0 and I'm not aware of anything else in terms of lower bounds.
Moreover, as data_interfaces is used by many charms that we don't have a control on, I would not be keen on forcing a higher minimum version.

However I think that we should indeed have a conditional logic fort that based on the ops version!

[dwilding]

Thanks @Gu1nness, that sounds good to me! Would you like me to have a go at a PR for checking the Ops version? Just let me know how I can help further 🙂

[Gu1nness]

If you have some time to do it, please do!
Otherwise I'll do it, it should be a quick one.

[dragomirp]

Hi, @dwilding, @Gu1nness, we discussed this at the Data office hours. We will give it a go on some of our charms and increase the ops pydep if there's no issues. ops 2 should still be working on Juju 2.9 and there was a CVE for ops, so most charms should be using at least 2.15 either way. Sorry for the late response.

[dwilding]

Thanks @dragomirp, and no worries at all. (I was off earlier this week, so I'm just catching up with this)

I'll hold off doing a PR for now, while you give it a go in your charms, but I'm very to help later if needed.

BTW, as a perhaps related heads up, Charm Tech will soon be releasing Ops 3, which will drop support for Python 3.8. I'm not sure whether that's directly related to this discussion, but I thought I should let you know. Ben posted more details in Matrix here: https://matrix.to/#/!xdClnUGkurzjxqiQcN:ubuntu.com/$lD8rM5werEMMmgJcTBdKKG-ub4m1TIlxkJ1OeJ4gIvc?via=ubuntu.com&via=matrix.org&via=lgp.sh