Customize docker image - install package

Hi

I would like to deploy crossbar docker image with some additionnal python package (eg jwt)

I tried the following docker file
FROM crossbario/crossbar
RUN pip install jwt
ENTRYPOINT [“crossbar”]
CMD [ “start”, “–cbdir”, “/node/.crossbar”]

and the docker build process seems ok
but my component does not find the jwt package and the image refuses to start

any hint ?
thanks

a “USER root” line before the RUN pip install solved my issue