Images should pull from the appropriate minimal base image - e.g. should use python:3.8-alpine minimal base image in most cases.
Dockerfiles should minimize image size - this means any time a package is installed with apt or yum or pip care should be taken to ensure that the cache is either not used or cleaned after install:
FROM python:3.8
RUN pip3 install invoke && pip3 cache purge
FROM python:3.8
RUN pip3 install invoke
RUN mkdir /{{ cookiecutter.project_name }}
COPY {{ cookiecutter.project_name }}/ /{{ cookiecutter.project_name }}/{{ cookiecutter.project_name }}/
COPY tasks.py setup.py *.cfg configurations/ *.txt {{ cookiecutter.project_name }}/
WORKDIR /{{ cookiecutter.project_name }}
# Invoke install installs Python packages, so clean pip cache here
RUN invoke install && pip3 cache purge
ENTRYPOINT ["{{ cookiecutter.project_name }}", "--help"]