I had a node with docker installed - yet docker workflow was failing with
yet docker was available on this node and in the path (as verified by sh 'which docker;docker version'
It transpired that docker-workflow was spinning up another node unescearily and this node did not have docker installed - hence the failure.
After some discussion with Jesse Glick we found that the node with docker on did not set the HOME environment variable.
The workaround was to wrap the docker commands with withEnv(['HOME='+pwd()]).
The plugin should explicitly state why it is spawing a new node - to help the user understand, and should probably not rely on the HOME environment variable being set to determine if it can use docker