Fatal error(call to a member function rpush..) after install Emoncms Module "BACKUP"

Emoncms
1

I used this link “GitHub - emoncms/backup: emoncms backup module” to help me for install the backup module in my emoncms interface. in the Export when i click on “Create backup” i have this ERROR.

IMG_20180704_101033
IMG_20180704_1010331834×465 150 KB

Thank you for your help.