PyDrive backend broken, needs update to oauth2client library

[Dario Giovannetti]

pydrivebackend.py#L36 [1] tries to import SignedJwtAssertionCredentials from oauth2client.client, but that class has recently been removed [2], thus breaking the PyDrive back-end.

The new class to be used is "OAuth2Credentials": simply replacing the class name in pydrivebackend.py will restore the functionality.

[1] http://bazaar.launchpad.net/~duplicity-team/duplicity/0.7-series/view/head:/duplicity/backends/pydrivebackend.py#L36
[2] https://github.com/google/oauth2client/commit/dcd20c9375308979e45ae280ec102a28d2ca60d1