I very seldom have issues, so I thought that I would document the aforementioned error message (see title) at the close of an update, last evening. All of the other relevant threads on this topic are closed at the moment, so piling on is not an option. Therefore, here we are.
I had a look at the existing threads and particularly liked this one:
… as, since when does a little maintenance go amiss, eh? That bit of maintenance behind me and after rebooting and updating once again, everything seems to be back to normal. Disaster averted; no need to roll back the system.
Sure, you can delete python-future (and eventually, we no doubt will have no further use for it) as some have done, but as the Endeavour devs have deemed it useful / necessary, by installing it on my machine, I have sought to preserve it … at least for the time being.
As this is purely an informational / philosophical post, I have preemptively marked it solved.