Failing to store a token in the keyring results in a verification email

Under certain circumstances, when you sign in using your standard SSO creds ubuntu-sso-client will say it has sent you a verification email, even though your email is already verified. What's worse, this verification email is then never sent/received.

nessita pointed at the following lines of code:

main.py:197:
            if is_validated:
                # pylint: disable=E1101
                d = Keyring().set_credentials(app_name, credentials)
                d.addCallback(lambda _: self.LoggedIn(app_name, email))
                d.addErrback(lambda _: self.UserNotValidated(app_name, email))

That say the real problem is that the app is failing to store the newly created token in the keyring, and is then emitting UserNotValidated (instead of LoginError), that triggers the message saying a verification email has been sent. This email is then not sent at all, as the email is actually already verified.

The other (underlying) question is why the keyring is refusing to store the credentials at all.