Finally found something, as CI started to fail with a different error (which luckily contained a useable stacktrace). I am using broccoli-strip-debug and something causes it to fail. If I remove it, my build runs through again.
ember-cli-build.js:
let tree = app.toTree();
if (app.env === 'production') {
console.log('stripping debug statements...');
let stripDebug = require('broccoli-strip-debug');
tree = new stripDebug(tree);
console.log('done stripping debug statements...');
}
What’s quite strange to me is that the log statements are printed at the beginning of the build, however, the build fails after doing a lot of other stuff.