Prefect: remove version ceilings on prefect's dependencies?

[jameslamb]

Current behavior

Today, prefect requires that you have a cloudpickle version older than v 1.5.0:

https://github.com/PrefectHQ/prefect/blob/214b2944c0b49eaac0117e06e7fc1d0dabe408fc/requirements.txt#L2

I noticed this through a CI failure today, because cloudpickle did a 1.5.0 release yesterday

Why is this version ceiling in place? Is there a particular incompatibility that the maintainers here knew to anticipate in 1.5.0?

It looks like this was done automatically by a bot: https://github.com/PrefectHQ/prefect/commit/0ff0ce9f0700142dc2f4d8f875768d85d654fc48

Proposed behavior

I think it would be a better user experience to only use a ceiling to catch new _major_ versions of *cloudpickle(cloudpickle<2.0). I can't tell from [the repo](https://github.com/cloudpipe/cloudpickle) ifcloudpickle` follows semantic versioning, but if they do then there should only be breaking changes in major versions.

Thanks for your time and consideration!

[joshmeek]

@jameslamb I think it should be fine to bump up the upper version! We use dependabot for managing our dependencies and it hasn't caught the new version yet so we can bump manually.

[jameslamb]

Repurposing this issue, per https://github.com/PrefectHQ/prefect/pull/2911#discussion_r449216869.

The question:

should prefect remove version ceilings in its requirements.txt?

[jameslamb]

blegh sorry, the fixes() in my commit message closed this. It should probably be re-opened since it's been repurposed for a broader discussion

[cicdw]

FWIW I'm cool with this. As @joshmeek has pointed out in an offline convo we probably want to keep marshmallow and croniter bounded above due to being bit in the past, but otherwise we were probably being overly cautious with the upper bounds on everything.