Cannot show Automatic Strong Passwords - iCloud Keychain is disabled

[AutoFill] Cannot show Automatic Strong Passwords for app bundleID: your.bundle.id due to error: iCloud Keychain is disabled

This error occurs when the system's user doesn't have iCloud Keychain enabled.  This will often be the case on the Simulator.  Try it on one of your devices and see what happens.  I received this message on one of my devices where iCloud Keychain is enabled:

[AutoFill] Cannot show Automatic Strong Passwords for app bundleID: your.bundle.id due to error: Cannot save passwords for this app. Make sure you have set up Associated Domains for your app and AutoFill Passwords is enabled in Settings

So this is Apple's cool AutoFill feature... these steps should enable it for you.