Avoid AngularJS circular dependency error when using $state in a HTTP interceptor

auth-interceptor.service.js

angular
    .module('app')
    .factory('AuthInterceptor', AuthInterceptor);

function AuthInterceptor($injector, $q) {
    var $state;

    var service = {
        responseError: responseError
    };

    return service;

    function responseError(rejection) {
        $state = $state || $injector.get('$state');

        if (rejection.status === 401 && rejection.config.url !== '/login') {
            $state.go('login');
        }

        return $q.reject(rejection);
    }
}