Class 'League\OAuth2\Client\Provider\AbstractProvider' not found in /Users/mac/chain/Application/Libraries/Oauth2-github-master/src/Provider/Github.php on line 10
It looks like you are trying to run this library as a standalone project. It is intended to be run within an existing project that uses composer to load dependencies.
Class 'League\OAuth2\Client\Provider\AbstractProvider' not found in /Users/mac/chain/Application/Libraries/Oauth2-github-master/src/Provider/Github.php on line 10