docker run not working: no container created despite making container image - python-3.x

Question

Summary
docker run doesn't seem to build a container (but it also doesn't throw an error) despite docker build successfully building the container image.
Input and Output
1. Successful docker image creation..
$ docker build -t minitwitter:latest .
...
Successfully built da191988e0db
Successfully tagged minitwitter:latest
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
minitwitter latest da191988e0db 6 seconds ago 173MB
python 3.7-alpine b11d2a09763f 9 days ago 98.8MB
2. ..and docker run completes without error..
$ docker run --name minitwitter -d -p 8000:5000 --rm minitwitter:latest
e8835f1b4c72c8e1a8736589c74d56ee2d12ec7bcfb4695531759fb1c2cf0e48
3. ..but docker container doesn't seem to exist.
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
And navigating to the port where the app should be exposed, http://localhost:8000, returns the connection error ERR_CONNECTION_REFUSED.
Docker file, boot.sh
The Dockerfile and boot.sh files are pretty simple I think:
Dockerfile
FROM python:3.7-alpine
RUN adduser -D minitwitter
WORKDIR /home/minitwitter
COPY requirements.txt requirements.txt
RUN python -m venv env
RUN env/bin/pip install -r requirements.txt
RUN env/bin/pip install gunicorn
COPY app app
COPY migrations migrations
COPY minitwitter.py config.py boot.sh ./
RUN chmod a+x boot.sh
ENV FLASK_APP minitwitter.py
RUN chown -R minitwitter:minitwitter ./
USER minitwitter
EXPOSE 5000
ENTRYPOINT ["./boot.sh"]
boot.sh
# BOOTS A DOCKER CONTAINER
#!/bin/sh
source env/bin/activate
flask db upgrade
exec gunicorn -b :5000 --access-logfile - --error-logfile - minitwitter:app

Answer 1

Place the 'shebang' -- #!/bin/sh -- on the first line of the boot.sh shell script.
How I found this answer: This blog post which refers to this Stackoverflow post.
The problem: the original script has a comment on the first line and the shebang on the second line.
Note: The title of the 'Question' is misleading: a docker container was built. The container, however, was short-lived and given I used the -rm option in the docker run command, the container was deleted after it terminated within 2 seconds; this is why it didn't appear in the docker images -a command.