Docker: Error pushing to registry unsupported protocol scheme ""

Symptom

You are trying to push a docker image to Nexus Repository 3 and Docker complains with a message similar to:

Error pushing to registry: Put /v2/ubuntu/blobs/uploads/81ad3e90-544a-4bf6-88bf-acd92b479f69?digest=sha256%3Aa3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4: unsupported protocol scheme ""

Cause

This is a known issue that occurs when using Docker 1.7.1 (and probably earlier) with Nexus Repository 3. 

Solution

Upgrade to Docker 1.8.0 or later to solve this, version 1.8.0 is the minimum version supported by Nexus Repository 3.