title: In setup.py, how to run a system command before any pip install?
body: <p>I am creating a Python package with <code>setup.py</code>, and I need to run certain shell commands <em>before</em> pip attempts to install dependencies.  In fact, I need these commands to run <em>before</em> setuptools makes network calls to PyPI.</p>
  <p>(The nitty gritty context is that the system installing this package has an internet gateway which requires a certificate to be installed.  I need to apply this system change before setuptools reaches out to the internet)</p>
  <p>I'm aware of <code>cmdclass</code> -- do those commands run <em>before</em> the <code>install_requires</code> stage?</p>