I searched the whole drupal directory but I didn't find the autoload.php file. I see the error when enabling modules using drush on the command line.
Here is the exact error
include(sites/all/modules/contrib/guzzle/vendor/autoload.php): failed to open stream: No such file or directory composer_autoload.module:24 [warning] include(): Failed opening 'sites/all/modules/contrib/guzzle/vendor/autoload.php' for inclusion (include_path='.:/usr/share/php:/usr/share/pear') [warning] composer_autoload.module:24