Providing compatibility with Python 3.10

[forman]

Majority of issues come from outdated moto. Now, with current moto >=4, we run into aio-libs/aiobotocore#755 with no obvious solution.

Closes #583

Checklist:

• Add unit tests and/or doctests in docstrings
• Changes documented in CHANGES.md (will add after merge, so we don't need CI once more)
• AppVeyor CI passes
• Test coverage remains or increases (target 100%)

[TonioF]

Looks good. Do these changes change anything about this: https://github.com/dcs4cop/xcube/blob/cc3690c6ad889121b66511ad7a08c384a1ba5ac2/test/core/store/fs/test_subset.py#L164 , though?

[pont-us]

Approved, with one optional suggestion.

[pont-us]

Suggested change

	- python >=3.8
	- python >=3.8,<3.11

Currently, creating an xcube environment with the one-sided >=3.8 limit installs Python 3.10, I assume because something in the dependencies is currently requiring python <3.11. That dependency will one day suddenly start supporting Python 3.11 and new xcube environments will start getting Python 3.11 by default with no changes on our side. That seems dangerous, so I suggest including the upper limit, but I leave the decision to you.

[TonioF]

something in the dependencies is currently requiring python <3.11

It would be interesting to know what that something is.

[pont-us]

It would be interesting to know what that something is.

Agreed -- I considered investigating, but decided against it since explorations of conda dependency structures can get quite time-consuming.

[forman]

So you know, Python 3.11 is not working?

[forman]

If not, we stay with python >=3.8 and fix any issues with 3.11 when they occur.

[pont-us]

I don't know that Python 3.11 is not working, but I also don't know how to test that it will work. So if you want to take the chance we can leave it without the upper limit :)

[forman]

Looks good. Do these changes change anything about this:

I don't know. But we should find out after merging.