[cache] Fixing json.dumps for timestamp (#4240)
[cache] Fixing json.dumps for timestamp (#4240)


dmigo/incubator-superset,mistercrunch/panoramix,apache/incubator-superset,zhouyao1994/incubator-superset,airbnb/superset,dmigo/incubator-superset,apache/incubator-superset,dmigo/incubator-superset,apache/incubator-superset,apache/incubator-superset,mistercrunch/panoramix,mistercrunch/panoramix,airbnb/caravel,timifasubaa/incubator-superset,mistercrunch/panoramix,zhouyao1994/incubator-superset,timifasubaa/incubator-superset,timifasubaa/incubator-superset,dmigo/incubator-superset,airbnb/superset,apache/incubator-superset,zhouyao1994/incubator-superset,airbnb/caravel,zhouyao1994/incubator-superset,timifasubaa/incubator-superset,zhouyao1994/incubator-superset,airbnb/superset,airbnb/caravel,airbnb/superset,airbnb/caravel