Installing a python project using Poetry in a Docker container

Although this is not an answer, it is too long to fit within the comment section. It is rather a piece of advice:

• declare your ENV at the top of the Dockerfile to make it easier to read.
• merge the multiple RUN commands together to avoid creating useless intermediate layers. In the particular case of apt-get install, this will also prevent you from installing a package which dates back from the first "apt-get update". Indeed, since the command line has not changed Docker will not re-execute the command and thus not refresh the package list..
• avoid making a copy of all the files in "." when you previously copy some specific files to specific places..

Here, you Dockerfile could rather look like:

# pull official base image
FROM ubuntu:20.04

ENV PATH = "${PATH}:/home/poetry/bin"
ENV HOME=/home/app
ENV APP_HOME=/home/app/web

RUN apt-get -y update && \
    apt upgrade -y && \
    apt-get install -y \
        python3-pip \
        curl \
        netcat \
        gunicorn && \
    rm -fr /var/lib/apt/lists

# alias python2 to python3
RUN ln -s /usr/bin/python3 /usr/bin/python

# Install Poetry
RUN mkdir -p /home/poetry && \
    curl -sSL https://install.python-poetry.org | POETRY_HOME=/home/poetry python -

# Cleanup
RUN apt-get remove -y \
        curl && \
    apt-get clean

RUN pip install --upgrade pip && \
    pip install cryptography && \
    pip install psycopg2-binary

# create directory for the app user
# create the app user
# create the appropriate directories
RUN mkdir -p /home/app && \
    adduser --system --group app && \
    mkdir -p $APP_HOME/static-incdtim && \
    mkdir -p $APP_HOME/mediafiles

WORKDIR $APP_HOME

# copy project
COPY . $APP_HOME

# Install Python packages
RUN poetry config virtualenvs.create false && \
    poetry install --only main

# copy entrypoint-prod.sh
RUN cp $APP_HOME/entrypoint.incdtim.prod.sh $APP_HOME/entrypoint.sh && \
    chmod a+x $APP_HOME/entrypoint.sh && \
    chown -R app:app $APP_HOME

# change to the app user
USER app

# run entrypoint.prod.sh
ENTRYPOINT ["/home/app/web/entrypoint.sh"]

UPDATE:

Let's get back to your question. Having your program running okay when you "run it yourself" does not mean all the dependencies are met. Indeed, this can mean that your module has not been imported yet (and thus has not triggered the ModuleNotFoundError exception yet).

In order to validate this theory, you can either:

1. create a simple application which imports the failing module and then quits. If the import succeeds then there is something weird indeed.
2. list the installed modules with poetry show --latest. If the package is listed, then there is something weird indeed.

If none of the above indicates the module is installed, that just means the module is not installed and you should update your Dockerfile to install it.

NOTE: I do not know much about poetry, but you may want to have a list external dependencies to be met for your application. In the case of pip3, the list is expressed as a file named requirement.txt and can be installed with pip3 install -r requirement.txt.