根据Heroku支持人员，这是神奇的东西：

As per the Heroku support staff, this is the magic thing:

heroku config:add LANG=en_US.UTF-8

尽管 heroku控制台将继续报告字符串编码为 ASCII-8BIT ，您的实际应用将使用正确的编码运行，基于 LANG config var。
您可以通过这样做来加倍检查：

Although heroku console will keep reporting strings encoding as ASCII-8BIT, your actuall app will be running with the correct encoding, based on the LANG config var. You can double check that by doing this:

$ heroku run bash
Running bash attached to terminal... up, run.2
u20415@022e95bf-3ab6-4291-97b1-741f95e7fbda:/app$ irb
irb(main):001:0> "a".encoding
=> #<Encoding:UTF-8>