Constant popups for bla-bla wants access to bla-bla keychain e.g.  cloudd wants access to icloud keychain, local items keychain etc.

I have been going nuts with this bug (it IS a bug as it seems to be caused by unhandled corruption to the icloud keychain).  I've had it 3 times now and it keeps coming back. 

I'm basically almost constantly bombarded with requests to provide a password for any one of several combinations of the above error (different things needed access to different keychains).   When I provide my password, it either gives me an 'incorrect password' response (shaking) or accepts it then asks for it again.

I have tried to turn off iCloud, but I can't, it turns itself back on.  I'm guessing this was a sync issue originally, but it's well out of hand now.

I'm using a 2015 macbook pro with 10.12.3 (Sierra).
https://discussions.apple.com/thread/5680074?tstart=0

I got this from an answer on the Apple.com site link (above) after about 6 hours searching and trying different solutions.  It's the only one that hasn't shown at least one of those login prompts in the first 5 minutes.  Thanks to 'rccatalyst' for providing it.  I'm copying it here, because Apple support just hasn't worked for me. The thread linked above it 4 years old and yet it hasn't turned up in any of my FAQ/google/KB searches.

Open 'Terminal' and run the commands below.

cd ~/Library/Keychains

ls

(When you 'ls' here you will see a folder that contains a bunch of random number like so:
94ED610F-DD96-4ECF-A2BC-7D2F8653A464 (this number is unique on each system))

rm -rf 94ED610F-DD96-4ECF-A2BC-7D2F8653A464 (i.e. whatever your code is)

Now reboot your Mac.

When you log back in everything should be back to normal.