Manually configuring KWallet when it is not available doesn't (immediately) generate an error.
If you configure the KWallet backend...
...when KWallet is not available, an exception will be raised when attempting to retrieve a password:
File ".../eggs/keyring-0.5.1-py2.6.egg/keyring/backend.py", line 206, in get_password if kwallet.keyDoesNotExist(network, 'Python', key): AttributeError: 'NoneType' object has no attribute 'keyDoesNotExist'
Instead an error should be generated as soon as the configuration is acted upon (but not at import time -- doing work at import time isn't friendly).