ImportError: cannot import name SignedJwtAssertionCredentials

I had this problem today and had to roll back from oauth2client version 2.0 to version 1.5.2 with:

pip install oauth2client==1.5.2

It seems like you havn't installed pyopenssl. Install via easy_install pyopenssl.

Libraries oauth2client.client
if HAS_OPENSSL:
  # PyOpenSSL is not a prerequisite for oauth2client, so if it is missing then
  # don't create the SignedJwtAssertionCredentials or the verify_id_token()
  # method.

  class SignedJwtAssertionCredentials(AssertionCredentials):
....

The source repository was recently updated, to make use of the new code:

from apiclient.discovery import build
from oauth2client.service_account import ServiceAccountCredentials

...