… I guess I’m not sharing any news here that the docs lack, at least those ones which are getting linked from the new validation. They refer to version 1 (in hypertext references) and version 2 (in their wording).
so this contradicts a lot and makes it hard to fully understand and to find out what to address highlighted by the validation and what to not touch despite infos/warnings.
Me personally was hitting an issue on skipping clean. I had that true earlier, then the new validator told me on the build configuration pane, I can (safely) drop it. Take that “safely” not for granted, I did look around v1 / v2; clean, why this changed in v2, that I can opt-in in v2 with some version number specified in the travis.yml - whatever - all sounded to me in the end I can safely "just"™ remove the skip cleanup.
guess what happend. next tagged release without build artifacts - so no release. 
as the change was recent, this was easy to fix - just skip cleanup back in, changed the tags revision, force-pushed and all well with github + travis + dpl v1.
so my “opt-in” was short. well, learned, I never was in. it was v1 all the time.
in short: the validator betrayed me. not good 
perhaps you can make it more visible on the configuration tab (I love much to see a validator in there, even if it’s not a perfect one, this is much much much better than having a validator more far away) that the validation is about v2 in part and provide a link on how to migrate to v2.