Started getting this error yesterday, there have been no recent changes to config.yml or fastfile
You have not shared any detail about your environment, but the error is likely to be caused by the version of fastlane that is being used.
It has shown up in the past, as this report indicates
That makes some sense, but I have been unable to update the fastlane version on circle, is that not something that circle ci has to update on their image?
Without more details about the environment you are running (such as the image used) I can not really add much more.