Login with facebook fails if user denies access

[alexef]

Stack trace:

Exception on /login/facebook [GET]
Traceback (most recent call last):
  File "/home/../pybox/local/lib/python2.7/site-packages/flask/app.py", line 1687, in wsgi_app
    response = self.full_dispatch_request()
 ...
  File "/home/../pybox/local/lib/python2.7/site-packages/flask_social/views.py", line 205, in login_callback
    response, query = provider.authorized_handler(login)()
TypeError: 'BaseResponse' object is not iterable