user-canceling of KDE Wallet dialogs causes unhandled exception
Upon import of kwallet.backends (which is done upon import of kwallet), the KDE Wallet modules are imported and if the import succeeds the wallet is opened.
Opening the wallet will sometimes (if the wallet hasn't been opened in this session) request a password to unlock the wallet or (if the user hasn't granted perminant access to this application) ask if the application is allowed to access the wallet.
If the user declines either of these dialogs an exception will be raised because kwallet is None and a method call is attempted on it.
I've attached a fix for this problem, with tests.