Installation Failing with ANSI_WARNINGS and CONCAT_NULL_YIELDS_NULL Errors

A couple of weeks ago, we had an unusual support case: upgrading two of our products, Visual Studio Integration Toolkit and GP Power Tools, was failing with a SQL Server error I had never seen before.
The errors only occurred on the customer’s live system, but the install worked fine on their development system. Eventually the cause for the issue was identified.
Today, my good friend Beat Bucher, had the same error and I was able to tell him the cause straight away. Read on for a full explanation.
