Plankton always create a .plankton directory inside the workspace.
When it is running from within a container, this directory is created with root user.
So, to delete it on the host, you must be a sudo user.
How to run the container with the same user on the host?
I have tried these options:
--user 1001:1001
-v /etc/passwd:/etc/passwd:ro
--group-add docker
But did not work.