lib/runner/request-helpers-presend.js
function (config, cb) {
                if (config) {
                    return cb(null, config);
                }

                return _.isFunction(run.options.systemProxy) ? run.options.systemProxy(url, cb) : cb(null, undefined);
            }
function (config, cb) {
                if (config) {
                    return cb(null, config);
                }

                return _.isFunction(run.options.systemProxy) ? run.options.systemProxy(url, cb) : cb(null, undefined);
            }
function ( config , cb ) { if ( config ) { return cb ( null , config ) ; } return _ . isFunction ( run . options . systemProxy ) ? run . options . systemProxy ( url , cb ) : cb ( null , undefined ) ; }
fallback to system proxy
fallback to system proxy