Don't require a 'OPENID_SSO_SERVER_URL' setting for testing

On line 132 of test_views.py the test tries to get the current setting for OPENID_SSO_SERVER_URL, but if none is set, the test fails. It should use a default like the lines before it:

self.old_sso_server_url = getattr(settings, 'OPENID_SSO_SERVER_URL', None)

instead of:

self.old_sso_server_url = getattr(settings, 'OPENID_SSO_SERVER_URL')