OpenSlides 2.3 is Always in OfflineMode

I opened the same ticker in OpenSlides/OpenSlides #4208. There @tsiegleauq commented, I should address to this project. IMHO that's wrong, because I don't use your Dockerfile and I think the problem is absolutely not related to docker. But anyway, I follow his recommendation, here is my problem:

grafik

I try to run OpenSlides 2.3 (the current stable release) in docker.

Dockerfile:

FROM mwaeckerlin/base
ENV VERSION                     "2.3"
ENV SOURCE                      "https://files.openslides.org/releases/${VERSION}/openslides-${VERSION}.tar.gz"
RUN apk add --no-cache --purge --clean-protected -u python3 python3-dev gcc libc-dev
WORKDIR /tmp
RUN wget -qO- $SOURCE | tar xz
WORKDIR /tmp/openslides-${VERSION}
RUN python3 setup.py install

USER ${RUN_USER}
CMD openslides start --local-installation

EXPOSE 8000

Compile it and run:

docker run -it --rm --name openslides -p 8000:8000 -u root mwaeckerlin/openslides openslides

So basically, the installation is as follows:

get an Alpine Linux (the same problem occurs in Ubuntu too)
install python3, python3-dev, gcc and libc-dev
download and extract https://files.openslides.org/releases/2.3/openslides-2.3.tar.gz
run python3 setup.py install
run openslides start --local-installation
connect to http://localhost:8000
enter user: admin, password: admin

Then you always get the error message: Offline mode: You can use OpenSlides but changes are not saved.

What's the problem?

OpenSlides / openslides-docker

OpenSlides 2.3 is Always in OfflineMode #9