code: function(err, r, b) {
        if (err) throw err;
        try {
          fs.unlink(keyname, this.parallel());
          fs.unlink(keyname + ".pub", this.parallel());
        } catch(e) {
          // do nothing
        };
        console.log("Heroku SSH keypair deleted from local FS");
        callback(err, this.privkey, this.pubkey, this.user_host_field);
      }
docs: SSH key has been added, unlink files