Try temporary work around for Drone build bug: https://github.com/drone-plugins/drone-docker/pull/327

.drone.yml

@@ -70,7 +70,9 @@ name: documentation
 
 steps:
 - name: build
-  image: plugins/docker
+  #image: plugins/docker
+  # Temporary work-around for https://github.com/drone-plugins/drone-docker/pull/327
+  image: techknowlogick/drone-docker
   settings:
     username:
       from_secret: docker_username