You can customize your pip.conf to point to a custom pypi repository
Sometimes a pip user may want to install a python package from a repository other than http://pypi.python.org/simple/.
ONAP has a staging repository in nexus3 for example at https://nexus3.onap.org/repository/PyPi.staging/.
By default, when you "pip install" it pulls from the public pypi repo, but if you want to pull from a custom repo there are 3 ways to do so (listed in order of precedence):
By passing a CLI flag to specify a custom index url
By setting an environment variable
By specifying in a custom pip.conf file