Missing Pages library from Publishing site – Upgrade blocker

I wanted to describe an upgrade error I ran across the other day in a SharePoint 2016 site that needed to be cleared in order for the content database to be upgraded correctly. First, the error I received when trying to do Upgrade-SPContentDatabase: Feature upgrade action ‘CustomUpgradeAction.Activate404ErrorPage’ threw an exception upgrading Feature ‘Publishing’ (Id: 15/’22a9ef51-737b-4ff2-9346-694633fe4416′) […]