Librato metrics failing due to improper source names

[SergeyKuryanov]

The Librato team let us know there are many failing entries due to invalid data in the source field. The example given was:

Response: {"errors":{"params":{"source":["ejenner11@red-larousse.mx is not a valid source name"]}},"request_time":1476916671}, Body: {"counters":[{"value":1,"measure_time":1476916671,"source":"ejenner11@red-larousse.mx","name":"cs.live.larousse-red_larousse-2-g7.open"},{"value":0,"measure_time":1476916671,"source":"ejenner11@red-larousse.mx","name":"cs.live.larousse-red_larousse-2-g7.pageview"}]}

Sources should be text and '-', '_' only so the '@' in the email would cause this to fail.