Attempt to fix dispatcher stats thread exception (#13478)

* Attempt to fix dispatcher stats thread exception

* catch both exceptions

* Make it work when redis module does not exist

* fix style

LibreNMS/service.py

@@ -26,6 +26,14 @@ try:
 except ImportError:
     pass
 
+try:
+    from redis.exceptions import ConnectionError as RedisConnectionError
+except ImportError:
+
+    class RedisConnectionError(Exception):
+        pass
+
+
 logger = logging.getLogger(__name__)
 
 
@@ -844,7 +852,7 @@ class Service:
                         getattr(self.config, worker_type).frequency,
                     )
                 )
-        except pymysql.err.Error:
+        except (pymysql.err.Error, ConnectionResetError, RedisConnectionError):
             logger.critical(
                 "Unable to log performance statistics - is the database still online?",
                 exc_info=True,