flask-sslify | Force SSL on your Flask app | Platform As A Service library

Your environment does not have access to an installation of wheel. You should be able to resolve this by adding the line:

RUN pip install wheel

to your dockerfile before you attempt to install your requirements file.

Edit: I missed that virtual environments were being utilized here. I would argue that using a virtual environment is unnecessary in this case unless the OP is using their docker instance to run multiple python applications in parallel. There are cases to be made for using this pattern, though that does not appear to be the case here. As such, my suggestion would be to do away with venv altogether and simply install all dependencies inside the docker instance python installation, which would convert every venv/bin/pip call to a simple pip call.