Poetry docker file that can support private git repository packages

poetry_dockerfile

# syntax=docker/dockerfile:experimental

FROM python:3.7-slim AS base

# ENV LANG=C.UTF-8  # Sets utf-8 encoding for Python et al
# ENV PYTHONDONTWRITEBYTECODE=1  # Turns off writing .pyc files; superfluous on an ephemeral container.
# ENV PYTHONUNBUFFERED=1  # Seems to speed things up

ENV PYTHONUNBUFFERED=1 \
    PYTHONDONTWRITEBYTECODE=1 \
    LANG=C.UTF-8 \
    PIP_NO_CACHE_DIR=off \
    PIP_DISABLE_PIP_VERSION_CHECK=on \
    PIP_DEFAULT_TIMEOUT=100 \
    POETRY_PATH=/opt/poetry \
    VENV_PATH=/opt/venv \
    POETRY_VERSION=1.0.0

# Ensures that the python and pip executables used
# in the image will be those from our virtualenv.
ENV PATH="$POETRY_PATH/bin:$VENV_PATH/bin:$PATH" \
    PYTHONPATH=/app

RUN apt-get -qy update && apt-get install --no-install-recommends -y git libev-dev

FROM base as poetrydev

RUN apt-get update \
    && apt-get install --no-install-recommends -y \
    # deps for installing poetry
    curl \
    # deps for building python deps
    build-essential \
    # deps for using ssh
    openssh-client \
    \
    # install poetry - uses $POETRY_VERSION internally
    && curl -sSL https://raw.githubusercontent.com/sdispater/poetry/master/get-poetry.py | python \
    && mv /root/.poetry $POETRY_PATH \
    && poetry --version \
    \
    # configure poetry & make a virtualenv ahead of time since we only need one
    && python -m venv $VENV_PATH \
    && poetry config virtualenvs.create false \
    \
    # cleanup
    && rm -rf /var/lib/apt/lists/*

WORKDIR /venv_build

COPY poetry.lock pyproject.toml ./

RUN mkdir -p -m 0600 ~/.ssh && ssh-keyscan github.com >> ~/.ssh/known_hosts
RUN --mount=type=ssh poetry install --no-interaction --no-ansi -vvv


# Dev version of Docker image
FROM base AS dev

WORKDIR /app
EXPOSE 80

# Install OS package dependencies.
# Do all of this in one RUN to limit final image size.
RUN rm -rf /var/cache/apt/* /var/lib/apt/lists/*

COPY --from=poetrydev $VENV_PATH $VENV_PATH
COPY ./app /app

CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--debug", "--port", "80", "--reload-dir", "CHANGE_ME_DIR_NAME"]

Yes.
I have not tried further to solve the problem, as it is not too important for me at the moment.
If I get to it and find a solution, I will post it here.