Add "test" mode to pep

[jcalderin]

For security reasons, its good to dont give any information about the internal errors (bad requests, bad auth, deny access, etc...).

But, for tests porpouses, is "nice to have" a "test" mode of the app. In this mode, the response give detailed information about what happend with the request in the integration process with Keystone and AccessControl

Effort: 1 man day