Error while sending request to Stackdriver ... unsupported protocol scheme """

I'm getting this error logged every ~30 seconds: `Error while sending request to Stackdriver Post /v3/projects/{my project}/timeSeries?alt=json: unsupported protocol scheme """`

I've just been watching my kube logs via the `kubectl log` CLI this whole time and this wasn't appearing in any of those logs. All my services are working as expected. But when I checked GCP logs interface on the website, apparently this has been going on for at least 1 week now, perhaps longer.

Any ideas?