Error when rebuild. Can't fetch from https://rubygems.org

[pmusaraj (Penar Musaraj)]

@cuo_wu

HINT: The plugin 'discourse-solved' is now bundled with Discourse and should not be included in your container configuration.
Remove the line 'git clone https://github.com/discourse/discourse-solved' from your containers/app.yml file, then try again.

Did you try doing this and running the rebuild again?