omab/django-social-auth — pull request #541 by maxgrosse (2012-12-05 09:33:39+00:00)
Title: Handle AuthCanceled exception to prevent uncaught exception when the user canceles login 

auth_complete might throw an AuthCanceled exception, which
eventually leads to an uncought exception / internal server error.
Now, in case the user canceles login, a correct message is set
and the user is redirected to the default LOGIN_ERROR_URL.

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We are getting internal server errors, when using Google OpenID and the user chooses "No Thanks" when google requests permission to handle over the login.
It looks like the same thing happens on the official demo site.