Never iCloud user: how to stop 'Your iCloud session has expired' messages in iTunes12?

I wouldn't have updated my iPad to iOS9 if I'd realized it was going to force an update to iTunes 12 (unbelievable that updating VIA iTunes 11 did not prompt a warning about this!). But actually the update iTunes 11 to 12 wasn't so bad except for one thing:

"Your iCloud session has expired."

Over and over, the prompts pop up to enter my AppleID. I have NEVER been an iCloud user, have not enabled iTunes Match or Apple Radio or any Cloud-dependent features, so obviously this prompt is about something else.

I see discussions about how to deal with this that make reference to doing something in Safari. I only use Safari for sites that will not work with Firefox, and I reset it to delete all data--cookies, history, cache--after every single use. It should not be relevant here.

In iTunes preferences, I have unchecked 'show Apple Music' and disabled everything I could see that might prompt connection to the cloud—Podcasts, Internet Radio, iTunes Store, Apple Music Connect, Shared Libraries. None of those steps have shut it up.

How do I get rid of this warning that requires me to sign into a nonexistent account?