Created by: gaearon
Our CI started failing, possibly after Jest released a 21.1.0 update.
After chatting to @byk our best guess is that because we didn't re-run Yarn after ejecting, the new script location (in the root /scripts folder rather than in node_modules/react-scripts/scripts) started picking up a different babel-core version that was previously being hoisted (6.x judging by the stack trace that has /lib/ in it) than the one react-scripts wanted (7.0 bridge).
Our current behavior always seemed weird to me (https://github.com/facebookincubator/create-react-app/issues/3356), and now that it's possibly causing bugs, I think we should try getting rid of that special case. Perhaps those issues in the TODO are not relevant anymore, or maybe we can find better fixes for them. Conceptually re-running yarn sounds like the only right thing to do.
I'm kind of shooting in the dark here so I also tried to update other Jest packages while we're at it.