pygraphviz installation into virtualenv mac

pygraphviz-install

# If you run into the the following error while installing pygraphviz into a virtualenv
# (on macOs, python3)
#
# pygraphviz/graphviz_wrap.c:2987:10: fatal error: 'graphviz/cgraph.h' file not found
# #include "graphviz/cgraph.h"
#         ^~~~~~~~~~~~~~~~~~~
# 1 error generated.
# error: command 'clang' failed with exit status 1

# - Install graphviz via brew
# - Download the pygraphviz source code
# - Compile the package without virtualenv: python3 setup.py build
# - Now do venv/bin/python setup.py install (with your virtualenv python)