AngularJS: Injecting service into a HTTP interceptor (Circular dependency)

This is what I ended up doing

  .config(['$httpProvider', function ($httpProvider) {
        //enable cors
        $httpProvider.defaults.useXDomain = true;

        $httpProvider.interceptors.push(['$location', '$injector', '$q', function ($location, $injector, $q) {
            return {
                'request': function (config) {

                    //injected manually to get around circular dependency problem.
                    var AuthService = $injector.get('Auth');

                    if (!AuthService.isAuthenticated()) {
                        $location.path('/login');
                    } else {
                        //add session_id as a bearer token in header of all outgoing HTTP requests.
                        var currentUser = AuthService.getCurrentUser();
                        if (currentUser !== null) {
                            var sessionId = AuthService.getCurrentUser().sessionId;
                            if (sessionId) {
                                config.headers.Authorization = 'Bearer ' + sessionId;
                            }
                        }
                    }

                    //add headers
                    return config;
                },
                'responseError': function (rejection) {
                    if (rejection.status === 401) {

                        //injected manually to get around circular dependency problem.
                        var AuthService = $injector.get('Auth');

                        //if server returns 401 despite user being authenticated on app side, it means session timed out on server
                        if (AuthService.isAuthenticated()) {
                            AuthService.appLogOut();
                        }
                        $location.path('/login');
                        return $q.reject(rejection);
                    }
                }
            };
        }]);
    }]);

Note: The $injector.get calls should be within the methods of the interceptor, if you try to use them elsewhere you will continue to get a circular dependency error in JS.