Fix config validation
Fix config validation

importlib.reload has side effects and apparently doesn't clean the cache as
expected by the original author, at least with Python 3.6. That results in an
import of the old config and thus breaks the validate_config function.

Deleting the cache in sys.modules is simpler and just works.

ramnes/qtile,qtile/qtile,tych0/qtile,qtile/qtile,tych0/qtile,ramnes/qtile