我在运行时遇到问题sudo apt-get update。我总是收到这个错误：
Err:1 https://deb.packager.io/gh/opf/openproject-ce xenial InRelease
Could not resolve host: deb.packager.io
Hit:2 http://us.archive.ubuntu.com/ubuntu xenial InRelease
Hit:3 http://us.archive.ubuntu.com/ubuntu xenial-updates InRelease
Hit:4 http://us.archive.ubuntu.com/ubuntu xenial-backports InRelease
Hit:5 http://ppa.launchpad.net/certbot/certbot/ubuntu xenial InRelease
Hit:6 http://security.ubuntu.com/ubuntu xenial-security InRelease
Hit:7 https://download.docker.com/linux/ubuntu xenial InRelease
Reading package lists... Done
W: Failed to fetch https://deb.packager.io/gh/opf/openproject-ce/dists/xenial/InRelease Could not resolve host: deb.packager.io
W: Some index files failed to download. They have been ignored, or old ones used instead.
我不明白为什么 apt 试图openproject在更新时获取包。我删除了整个包并运行了，sudo apt-get purge openproject但我仍然遇到相同的错误。
知道如何解决这个问题吗？