Update Dockerfile to be more simple

Remove virtualenv (useless with docker)
Be more close to official documentation : https://hub.docker.com/_/python

dockerfiles/Dockerfile

-FROM python:3-slim
+FROM python:3
+
+ENV PYTHONUNBUFFERED=1
 
 # Add french locale
 RUN apt update && \
@@ -7,20 +9,14 @@ RUN apt update && \
     sed -i '/^#.* fr_FR.UTF-8 /s/^#//' /etc/locale.gen && \
     locale-gen
 
-# Virtual env:
-ENV VIRTUAL_ENV=/opt/venv
-RUN python3 -m venv $VIRTUAL_ENV
-ENV PATH="$VIRTUAL_ENV/bin:$PATH"
-
 WORKDIR /home/app
 
-# Install dependencies:
-COPY requirements.txt /home/app/
-RUN pip install -r requirements.txt
+RUN pip install --upgrade pip
 
-# Setup volume to be able to dev application locally
-VOLUME /home/app
+COPY . /home/app
+
+RUN pip install -r requirements.txt
 
 # Run the application:
 EXPOSE 8080
-CMD ["./launch.sh", "0.0.0.0", "8080"]
+CMD python manage.py runserver 0.0.0.0:8080