All that I did was change childs to nodes (per https://github.com/postcss/postcss/blob/master/ChangeLog.md#40-duke-flauros), and the existing tests passed. I did not further analyze the upgrade, just looked for necessary syntax changes with the simple goal of making the existing tests pass. If you think that's good enough, then it's a pretty simple upgrade.
All that I did was change
childs
tonodes
(per https://github.com/postcss/postcss/blob/master/ChangeLog.md#40-duke-flauros), and the existing tests passed. I did not further analyze the upgrade, just looked for necessary syntax changes with the simple goal of making the existing tests pass. If you think that's good enough, then it's a pretty simple upgrade.