Information:

SensioLabsInsight was not able to boot your Symfony application. If you need to customize files or run commands to make it bootable, you can edit your SensioLabsInsight project configuration to override the default "pre_composer_script" and/or "post_composer_script" settings.

Solution

http://blog.insight.sensiolabs.com/2014/12/22/making-symfony-bootable-with-dbal-2-5.html