def dispatch(self, request):
        """
        View to handle final steps of OAuth based authentication where the user
        gets redirected back to from the service provider
        """
        login_done_url = reverse(self.adapter.provider_id + "_callback")
        client = self._get_client(request, login_done_url)
        if not client.is_valid():
            if 'denied' in request.GET:
                error = AuthError.CANCELLED
            else:
                error = AuthError.UNKNOWN
            extra_context = dict(oauth_client=client)
            return render_authentication_error(
                request,
                self.adapter.provider_id,
                error=error,
                extra_context=extra_context)
        app = self.adapter.get_provider().get_app(request)
        try:
            access_token = client.get_access_token()
            token = SocialToken(
                app=app,
                token=access_token['oauth_token'],
                # .get() -- e.g. Evernote does not feature a secret
                token_secret=access_token.get('oauth_token_secret', ''))
            login = self.adapter.complete_login(request,
                                                app,
                                                token,
                                                response=access_token)
            login.token = token
            login.state = SocialLogin.unstash_state(request)
            return complete_social_login(request, login)
        except OAuthError as e:
            return render_authentication_error(
                request,
                self.adapter.provider_id,
                exception=e)
View to handle final steps of OAuth based authentication where the user
        gets redirected back to from the service provider