Potentially related to #878 I'm working on a reactive charm. Recently, the `charmcraft pack` command has stopped working. This is the `charmcraft.yaml` file: ```yaml type: "charm" bases: - build-on: - name: "ubuntu" channel: "20.04" run-on: - name: "ubuntu" channel: "16.04" - name: "ubuntu" channel: "18.04" - name: "ubuntu" channel: "20.04" parts: charm: source: . plugin: reactive build-snaps: [charm] build-packages: - virtualenv - git ``` This is the `metadata.yaml` file: ```yaml name: jenkins display-name: Jenkins docs: https://discourse.charmhub.io/t/jenkins-docs-index/4831 summary: Jenkins Continuous Integration Server maintainers: - IS SRE <launchpad.net/~canonical-is-sre> description: > Jenkins is an extendable open source continuous integration server that monitors executions of repeated jobs. The focus of Jenkins is the building/testing of software project continuously, and monitoring executions of externally-run jobs. More information at http://jenkins-ci.org/. This charm provides the Jenkins master service, and when paired with the jenkins-slave charm provides an easy way to deploy Jenkins on Ubuntu server, and scale out Jenkins slaves. tags: - application_development - ops subordinate: false series: - xenial - bionic - focal provides: website: interface: http extension: interface: jenkins-extension scope: container optional: true nrpe-external-master: interface: nrpe-external-master scope: container requires: master: interface: jenkins-slave optional: true zuul: interface: zuul optional: true storage: jenkins: type: filesystem description: Jenkins data. location: /srv/mnt/jenkins ``` This is the log of the build where it seems that the installation of `Jinja2` fails because `markupsafe` is not installed: https://pastebin.canonical.com/p/xgKbsnvrwN/