Make file macro function to perform pip install

macro_example.make

# vim: set syntax=Makefile
# define at top of file
define PIP_INSTALL
    @if [ ! $(shell echo ${VIRTUAL_ENV}) ]; then \
        set +o nounset; \
        source ${VIRTUALENVPATH}/bin/activate; \
        set -o nounset; \
    fi; \
    cd external-code/ && pip install $1
endef

sprint: upsgrade-pip
  $(call PIP_INSTALL,-r requirements.txt --exists-action w -r requirements-sprint.txt)

install-jobs: upsgrade-pip
  $(call PIP_INSTALL,-r requirements.txt -r requirements-release.txt)