vendors/execa.js/isexe
    function isexe(path3, options, cb) {
      if (typeof options === "function") {
        cb = options;
        options = {};
      }
      if (!cb) {
        if (typeof Promise !== "function") {
          throw new TypeError("callback not provided");
        }
        return new Promise(function(resolve, reject) {
          isexe(path3, options || {}, function(er, is) {
            if (er) {
              reject(er);
            } else {
              resolve(is);
            }
          });
        });
      }
      core(path3, options || {}, function(er, is) {
        if (er) {
          if (er.code === "EACCES" || options && options.ignoreErrors) {
            er = null;
            is = false;
          }
        }
        cb(er, is);
      });
    }