Offer Python Latest (nightly master trunk build)

One of the features I love most about TravisCI is the ability to build my projects CI with top of Trunk Python (master branch). This allows me to know about deprecations etc. coming very early and have time to work on the fixes sooner.

Can actions look at supporting building a Trunk version nightly? Here is an example usage with Travis: https://github.com/facebookincubator/ptr/blob/master/.travis.yml#L16

Haven't dug in deep, but would also love to have the ability for this build to be able to fail and not flag CI failure, like the Travis config above does.

Thanks.

该 issue 没有指出任何 setup-python 文件或测试。首先检查 setup-python 仓库的入口点以及 facebookincubator/ptr 中链接的 Travis 配置，以了解 nightly Python master build 及其允许失败时的行为。完成的标准是：workflows 可以请求 nightly trunk build，而不会因为预期中的失败导致整个 CI 失败。