Sphinx 3.5 compatibility

[utzig]

• Allow working with newer Sphinx 3.5.0
• Add Sphinx 3.5.0 and change 3.4.x branch to 3.5.x in unit tests matrix. This should fix the broken CI.

This should fix the failures seen on #638 and #639

[utzig]

@vermeeren TBH I have not tested with Sphinx 3.5.0, haven't even seen it came out before just now. But I don't see a reason for it not working, and even if it has failures, it will need to be fixed anyway, so this should be fine.

[vermeeren]

@jakobandersen Any changes that you know of on the Sphinx side that need some adaptation over here? Seems fine to me as the CI is working nicely.

[jakobandersen]

No, I think it should work fine.
Though, if I understand correctly, the next major/minor release is going to be v4 (https://github.com/sphinx-doc/sphinx/milestone/74), but the suggested version constraint of course works as well. For that Sphinx release I suggest constraining only on the major versions, unless something unexpected comes up. Then it's only every year it needs a quick bump :-).

[vermeeren]

@jakobandersen Will do, thanks for the quick reply.

[jmckenna]

As this issue prevents those using Sphinx 3.5.0 + breathe, I'm kindly wondering when the next breathe release will be?

[jmckenna]

PS. Sphinx 3.5.1 was released moments ago...

[vermeeren]

@jmckenna I intended to release after the current 2 PRs had been merged, but I agree the compatibility update is needed earlier. Just released v4.27.0 containing this fix.

[jmckenna]

thanks @vermeeren ! I appreciate this.