WARNING: iOS upgrade pitfall: iCloud Keychain deleted because incompatible with Google Voice

If the SMS-capable phone number you provided when you first set up iCloud Keychain is a Google Voice number, the verification code Apple tries to send via SMS to this phone number will not arrive. When I contacted Apple Support, after upgrading my iPhone to 7.0.4, because I did not get the verification code, they did not help me complete iCloud Keychain setup, other than to guide me through steps that would delete my keychain and force me to start over.)