I appreciate your looking into this. I’ve been digging, also, and I think I may have found a key part of the problem: due to my App’s age, its Client code is running as Python 2, which does not have a ‘bytes’ type.
This still does not explain why the exact same code worked yesterday. Perhaps a Skulpt update occurred?
Option 1
With that in mind, upgrading this App to Client-side Python 3 looks like the obvious solution, and will probably be the best solution, long-term. (After all, we can’t expect our good friends at Anvil to support obsolete infrastructure forever.)
Unfortunately, the App’s sheer size (my forms\ folder contains 266 files), and my unfamiliarity with the new Packages layout (a prerequisite) may make that difficult.
Maybe when I can budget the time, I’ll try out the upgrade process on a clone of the App, and watch what happens to my local copy (via Git) of the clone’s files and folders, as a result.
Option 2
For now, instead of building the BlobMedia on the Client, with its Python 2 limitations, I’m just going to try building it on the Server, where the code runs in Python 3, and returning it from there to the Client.