RedisIntegration does not throw DidNotEnable when there is no redis module #735
Description
Most of integrations have ModuleDoesNotExist / ImportError try...except block throwing DidNotEnable exception (see: celery, flask, sqlalchemy).
RedisIntegration have redis module import inside setup_once method because of monkey-patching.
This causes some sort of problems during wide-range integrations autodetection.
