Comment 0 for bug 1942936

percona_utils.get_wresp_value(key)

can fail in cursor.execute(...) with an Exception but the logging is

```
unit-mysql-3: 15:53:19 ERROR unit.mysql/3.juju-log Failed to get '%s'
```

changing to

    except Exception as e:
        log("Failed to get key=%s '%s'" % (key, e), ERROR)
        return None

you can get a better log

```
unit-mysql-3: 15:58:33 ERROR unit.mysql/3.juju-log Failed to get key=wsrep_ready '(1146, "Table 'performance_schema.session_status' doesn't exist")'
```