Log exception for catching custom exception in init handler

For tracking error easily when custom exception is raised, log exception
as well before transitioning to failed state.

Signed-off-by: Chenxiong Qi <cqi@redhat.com>

module_build_service/scheduler/handlers/modules.py

@@ -157,6 +157,7 @@ def init(config, session, msg):
         build.transition(conf, models.BUILD_STATES["wait"])
     # Catch custom exceptions that we can expose to the user
     except (UnprocessableEntity, Forbidden, ValidationError, RuntimeError) as e:
+        log.exception(str(e))
         # Rollback changes underway
         session.rollback()
         build.transition(conf, models.BUILD_STATES["failed"], state_reason=str(e))