The [`pantheon-upstreams`](https://github.com/pantheon-upstreams/wordpress-composer-managed) repository has a [`.travis.yml`](https://github.com/pantheon-upstreams/wordpress-composer-managed/blob/main/.travis.yml) file that gets included in downstream sites but is not used for anything. This file should be removed (and likely needs to be removed from the `pantheon-upstreams` site manually.