graphics/py-cairo: Remove PYO_EXTENSION references

In D20352#438850, @dch wrote:

thanks koobs; however 0.9.0 is the last working version for python 2.7. Can we do a small bump (per my BZ patch) to 0.9.0, and wait for 2020/01/01 to move to 1.0.2? I'd prefer this as it will break anybody who hasn't gone through their own personal pycopalypse yet...

Add netbox changes that motivate these changes to the diff, it helps for everyone to have full context, especially if they're unfamiliar.

In D16716#434798, @matthew wrote:

In D16716#434707, @koobs wrote:

I have a WIP for pbr 5.2.0 pending (reverse dependents) QA

Is 5.x ok for the port you have that uses it? Which port/python package is it btw?

The port in question is ultimately devel/py-molecule -- however I think that it has since dropped the requirement for pbr in favour of setuptools-scm. (I need to update the py-molecule port it seems)

In D20161#434772, @koobs wrote:

What, multiple version specs (AND'd, not OR'd) are supported? If so, WOW.

I've recently been specifying max pinned versions to make future QA easier (grepping the tree), as it is a ridiculously laborious task to do manually, particularly for python ports with a large set of dependencies

What, multiple version specs (AND'd, not OR'd) are supported? If so, WOW.

arangodb32 and arangodb33 now exist in the tree

@loader This still needs to land?

py3-* ports are no longer being created.

D7581 committed/closed, can this progress now?

I have a WIP for pbr 5.2.0 pending (reverse dependents) QA

Committed in rP499073