Fix linting errors.

Author: stephrdev

cacheback/base.py

@@ -328,7 +328,7 @@ def async_refresh(self, *args, **kwargs):
                 ),
                 task_options=self.task_options
             )
-        except Exception as e:
+        except Exception:
             # Handle exceptions from talking to RabbitMQ - eg connection
             # refused.  When this happens, we try to run the task
             # synchronously.

cacheback/utils.py

@@ -17,7 +17,7 @@
 try:
     import django_rq
     from .rq_tasks import refresh_cache as rq_refresh_cache
-except ImportError as exc:
+except ImportError:
     django_rq = None
     rq_refresh_cache = None