^^&&^^

Edit File: AuthHandlerFactory.php

<?php
/**
 * Copyright 2015 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

namespace Google\AuthHandler;

use GuzzleHttp\Client;
use GuzzleHttp\ClientInterface;
use Exception;

class AuthHandlerFactory
{
  /**
   * Builds out a default http handler for the installed version of guzzle.
   *
   * @return Guzzle5AuthHandler|Guzzle6AuthHandler|Guzzle7AuthHandler
   * @throws Exception
   */
  public static function build($cache = null, array $cacheConfig = [])
  {
    $guzzleVersion = null;
    if (defined('\GuzzleHttp\ClientInterface::MAJOR_VERSION')) {
      $guzzleVersion = ClientInterface::MAJOR_VERSION;
    } elseif (defined('\GuzzleHttp\ClientInterface::VERSION')) {
      $guzzleVersion = (int) substr(ClientInterface::VERSION, 0, 1);
    }

switch ($guzzleVersion) {
      case 5:
        return new Guzzle5AuthHandler($cache, $cacheConfig);
      case 6:
        return new Guzzle6AuthHandler($cache, $cacheConfig);
      case 7:
        return new Guzzle7AuthHandler($cache, $cacheConfig);
      default:
        throw new Exception('Version not supported');
    }
  }
}