This is just a first level warning that the process UBD wishes a look inside keychain for something. At that point you have to go inside that keychain and check that all of the items do not let that process automatically or always access the contents(one by one for each item in the keychain). The tool for this looking is Keychain Access.
What you verified the things in the keychain are set properly you can go ahead and allow the opening of the keychain and it will then be able to just examine what is inside that keychain file by name.
In this case everything seems "on the up and up" because the ubiquity demon would quite reasonably want to look inside that keychain file just to see if you could be storing an iCloud account credentials. It doesn't mean it would get to read the password or anything encrypted about that iCloud account, it's just checking to see if an iCloud account could be stored in there.