We’ve been having lots of problems building over the past 24 hours which we tracked down to
herkou plugins:install heroku-pipelines The exact problem was that in heroku’s npm mirror a reference to a subdependency, validator, had become corrupted. Heroku’s cache of that item has now expired and we’ve verified we can install the plugin locally. On circleci it appears a cached copy is still being held somewhere, as evidenced by the error here https://circleci.com/gh/Financial-Times/next-article/1878 (note that this still happens even if we build without cache)
Do you have your own cache of packages from the heroku npm mirror? If so, could you please clear the broken entry for validator.