This pull request removed Zend_Registry from core by replacing it with an own simplistic Registry implementation in core/Registry.php.
I didn't yet comment the code in core/Registry, but will do so once merged.
Hm. That test failure is interesting. It shouldn't happen.
Nice change... Build failed maybe because you removed the file 2.0-a7.php ?
Guess there is an 'use Piwik\Registry' missing in FrontController.php
Good catch, but sadly not the reason for test failure. For some reason the with entry in the registry vanishes.
Auth entry that is