Web browser displays bare JSON object when bulk download has expired

[eecavanna]

In preparation for some scheduled downtime of the CFS filesystem used by the Portal's data proxy service, we have scaled down that data proxy service. As a result, data file downloads do not work. I wanted to know what users would see when they tried to download data files. So, I tried to download one, as shown here:

What I saw surprised me. Instead of seeing an error message within the context of the Data Portal UI, I saw a bare JSON object on a blank web page. Here is the error message (on left). On the right side of my screen is the "Network" tab of my web browser's DevTools.

The task here is to display an error message within the context of the Data Portal UI.