"npm ERR! Error: EACCES: permission denied" in Post Build Script

For the last year and a half, our team has been using a system where Unity Cloud creates a build, and then a post-build script installs the App Center CLI, and uploads the completed build to App Center. This system has worked well for us.

However, ever since the 19th of October, whenever Unity Cloud runs the post build script, we get this error:

npm ERR! Error: EACCES: permission denied

And it won’t upload to App Center any more.
What changed? How do we get our automated system working again?

Hi! This was a bug introduced with the latest Xcode. It should be fixed – let me know if this is still an issue for you @Ian-Underwood