Error when installing python3 packages in alpine

I'm not sure about the full list of dev-packages to build in the question, but it should be the following: g++ (GNU C++ standard library and compiler), python3-dev (python3 development files), libffi-dev (libffi development files) and openssl-dev (Toolkit for SSL v2/v3 and TLS v1 development files).

The Dockerfile is:

FROM alpine:3.7RUN apk add --no-cache --virtual .build-deps g++ python3-dev libffi-dev openssl-dev && \    apk add --no-cache --update python3 && \    pip3 install --upgrade pip setuptoolsRUN pip3 install pendulum service_identity

Apparently when upgrading pip with:

pip3 install --upgrade pip setuptools

I removed pip upgrading and installation worked. Now, I have been researching the correct way to upgrade pip on alpine and found a Dockerfile in a github repo that does this check:

if [ ! -e /usr/bin/pip ]; then ln -s pip3 /usr/bin/pip ; fi && \if [[ ! -e /usr/bin/python ]]; then ln -sf /usr/bin/python3 /usr/bin/python; fi && \

Which makes sure that pip3 is being referred when calling just pip command by doing a symbolic link on python and system binaries' directories.